It doesn't need to be done any special way, really. The episode thing could work, but Kaga pointed out some pitfalls of that model. You could just stage it so players are dropped into the game after the initial outpost is built (say very rudimentary defenses and houses that can be improved upon later), then start throwing events at them; bandits, monsters, famine, lack of essential supplies, whatever you want to do. No need to split it into specific episodes, just have it run as one continuous thing where stuff happens and the outpost grows or falls into ruin depending on how successful the players are at doing things. Call it an open-ended survival RP, outline the concept, and off you go with the interest check. No idea how much interest you'd get, but I wouldn't be surprised if there's a lot of people who like the idea of a more sedentary fantasy thing instead of the typical "go on an epic quest to retrieve the important artifact and defeat the big bad evil guy" thing.
Alternatively you could give it some particular but non-specific end goal if you wanted, like "grow the outpost into a safe colony city" or "grow the colony into a strong military fortress" or "grow the outpost into an independent city-state that breaks off from the motherland" or whatever, something that may not ever happen but is a reasonable goal for a little outpost to strive toward. Making it something that has many ways to approach it (making a safe colony city could be done by heavy militarization, or just heavy defenses with all the farming needed for sustenance done inside the walls, or strong alliances with nearby civilizations for protection, or razing the forests and destroying all monsters and wildlife to cull all threats, etc.) That nebulous goal, plus talking about and/or showing growth in the outpost after each event (probably via time skipping through times where the dwarves are peacefully building away), would be enough to give it a nice sense of continuity and progress I would think.
Okay, so, above that line are the reasonable normal roleplay ideas. While writing them I thought up a far more ambitious idea that may or may not interest you, more of a game system idea than an idea about how you should present the concept in an interest check. This could be used with any of the above suggestions since it's kind of a different thing, this the divider line to give it its own section.
If you want to go crazy with it you could try to build a system to emphasize the growing outpost aspect instead of hewing to traditional roleplay styles, basically merging the city/base building aspects of some strategy games (Warcraft and Starcraft and Banished, for example) with roleplaying. I feel like if you're going to do a roleplay about settlers then you really need a way to show the growth and development of that settlement, and some kind of point system is the best way to do it. You could work up a point system for food, money, wood, stone, iron, and other such supplies to show what the outpost has available. Some kind of basic map showing the layout of the outpost would be smart for this kind of thing as well, even if it's just a basic MS Paint thing, as deciding where to build new things could be important. It would probably be best to run this sort of game in rounds that represent certain amounts of time passing (a day or more for peaceful times maybe, and perhaps as short as 10 seconds for fighting) in which NPCs do a set amount of gathering and work and each player character can do a certain amount of stuff that has a larger impact. Let's say you make it an action point system, for simplicity and consistency. I'll give an example of what I mean by an action point system in a hider, since it'll be kind of long.
What I'm talking about with an action point system is static system where everyone gets X action points per Y period of time (preferably linked to the length of a standard round, with combat points having different rules). These action points would represent the time the player characters spend working each day, because if they're out there building an outpost then they would all be chipping in every day. You would have to work out how much a single point is worth for various actions, with the values determined purely for the sake of game balance. You can fudge the numbers quite a bit if you apply fantasy and game logic for the sake of balance and still keep it feeling reasonable. It may be kind of silly for it to take the same time to gather 1 unit of wood as to gather 1 unit of food, but the game would probably slow to a crawl if you made it so chopping down a tree and cutting it into useable planks takes a realistic amount of time.
Let's say you work it out so everyone gets 5 action points per day, and these points account for the time they're actually working on stuff to help the outpost for that day, with each point representing 2 hours of work for a 10 hour work day. If they want to spend a single point gathering wood, you could say that it gives the outpost 1 wood resource point. Another example would be going and hunting for food; let's say 1 action point spent hunting could give the city 3 food points (where maybe 1 food point = 1 person fed for an entire day). Or if they want to help build a structure you could say 1 action point gives 0.5 building points to the completion of that building, where depending on the size and complexity of the building it requires a certain amount of total building points and a certain amount of resource points to be completed. Let's say they wanna build a basic wood house, call it 5 wood resource and 10 building points to finish it; given the examples previously stated, five player characters could gather the resources for and build an entire house in one day if they used all their action points on it (1 each to gather wood at the start of the day, then 4 each on building for the rest of the day), which is kind of crazy honestly but it would make the players feel badass compared to NPCs even though all they did was build a simple house.
Speaking of NPCs, you could make the town NPCs each work on a similar system. Let's say you cut their base efficiency at all tasks in half, so player characters are twice as strong and fast and such as average NPCs. You could say there are four NPCs who go cut down trees all day with their own five action points, and each of them end up with 2.5 wood resource points, which would mean that each day the town gets 10 wood resource points even if the players do nothing with wood gathering. Similar could be done with building and food gathering and whatnot. This sort of thing would make even NPCs feel important to the outpost, since if one of them dies in a goblin attack or whatever then that's one less pair of hands bringing in resources or building things, so it would give the players further incentive to do the best they can for the outpost as a whole. If you wanted to give the players greater control you could allow them to assign NPC workers to various tasks, or you could handle this yourself.
Combat could be done in a similar way with points, and it would end up being rather similar to tabletop game combat. Say each round during combat is 10 seconds, and people get 5 action points for that as well. Say moving a certain amount of distance costs 1 point (ideally you should do such a thing with a basic grid map showing the battlefield, and you could say 1 action point moving lets you move X squares). Attacking with a small or medium sized melee weapon costs 2 points (1 for the time it takes to attack, 1 for recovery time); a large weapon attack would cost 3 points (to represent the longer swing and recovery time). Attacking with a bow could cost 2 points, with the ability to spend extra points before the attack for the sake of aiming to boost accuracy. If you use magic, you could have spell casting times represented by point cost. Boom, combat system done. Enemies should work on this same system as well, although you could adjust their point things based on their race and skills and such, like orcs and other big strong things could only need 2 points to use a big weapon, and elves could fire a bow for 1 point, that sorta thing. You could do combat either as all the players go and then all the enemies go (the easiest to organize), or work up some kind of initiative system and do a battle order where each person goes in turn based on their speed or whatever (the slightly more accurate but harder to organize way to do it). You could do a whole health and armor and accuracy and so on system to determine whether things hit or miss and how much damage they do, or you could just be lazy and decide what goes down each time with a simple six-sided dice roll (1 being total failure/miss, 6 being very well executed, roll an attack and defender dice for each attack attempt and whoever rolls higher wins that little exchange).
Alternatively, you could make combat an exception to the point system thing. You could have all combat come down to pure roleplay stuff, to pull away from the tabletop game feel. Either way could work with the rest of the point system, since combat is a very different thing than the work stuff that goes into building an outpost, so you could go with whatever you think fits the best.
This kind of point system would lend itself very well to a more strictly structured character sheet, similarly to a tabletop game character sheet. You could give players points to allocate in various skills (woodcutting, hunting, building, fighting, etc.) when they start, and they would give bonuses to those actions, like a point in woodcutting could mean they get one bonus wood per action point used to gather wood. This would allow greater individuality for the player characters, so they can specialize in things instead of being identical in their capabilities. If you were to do this, you could actually make the base levels for player and NPC characters doing work entirely identical, and let them stand out from the NPCs based on how they chose to build their character. You could also go further than just skill points, like making classes with special perks and skills (plus the ability to acquire new special abilities and such, say via spending action points to learn how to do these things) to bring in some RPG flair along with the RTS stuff.
Again, like combat, you could take or leave the point-heavy idea for character sheets whilst still using the point stuff for the outpost building and it could work just fine either way.
The sky's the limit with this kind of point system in place, really. You could keep things reasonable and down to earth, or you could let players become superhuman masters of whatever they wanna do, all while keeping the focus on building up the outpost instead of going on grand adventures. With various events and problems thrown into the mix, the point system could stay fun for quite a long time.
Though I've now gone on at length about how you could do a strict point system, I feel it's worth mentioning that you could use the whole point system idea without having it be the main focus of the roleplay. Players actually describing their work being done could be entirely optional. IC posts could be a line mentioning action point allocation, then on with roleplaying things where the players interact with each other or GM controlled NPCs. The roleplaying side of things would be largely socializing and character building stuff, by necessity with this concept of having everyone stuck in one place and building the outpost. You could always throw problems and events at the players that require standard roleplaying solutions to mix things up, of course. Say the blacksmith is having a feud with the stable master and refuses to make any more horseshoes while that guy remains in charge, and players are charged with solving the dispute in some way so that the needed horseshoes are back in production. That's a pretty simple problem that could be an issue for a growing outpost. Then you could have interactions with other nearby sentient beings, both positive and negative, that are all talking and interacting stuff unless it turns to combat. Fighting stuff could be done with point stuff or in the usual roleplaying free form style, as stated in the action points hider. You could just use the whole resources and action points thing as a way for players to have a direct hand in deciding how the outpost develops, something secondary to the roleplaying instead of something of equal or greater importance as might have been implied by how I described things.
You could also go so far as to boil down the point system into just a way to show the status of the outpost, and how players are impacting its health. You could cut it down to stats for food, building materials, and money on hand (either numbers or general things like 'low' or 'very high' to show how they're doing), cut out the whole player action points thing, and give regular updates to how the outpost is growing. The whole point system idea is really just a way to show the growth of the outpost, and you can do that without making the players directly interact with the work side of things. I happen to feel like giving players direct impact on all that makes it more fun for them, but you and others may disagree, thus the alternative presented.
