Okay, now that I'm home, let's start pumping out a few more details:
1. The standard races from the series and most of the abilities associated with them will still apply. However I do plan on adding a few things, particularly to the Earthlings so they don't feel like they are perpetually falling behind. And on the subject of races, I'm going to try and make each of the races feel as unique as possible, with each potentially having their own unique options available to them so that each might have their own appeal.
2. Saiyans. They are indeed a thing. No, they are not completely extinct, in fact there will be a few more of them present than in the canon series for reasons I will go over at a later time. However, I may implement a nerf here or there for the Saiyans to keep them from becoming as disgustingly overpowered as they got in the canon series.
3. Power Levels. This one's a bit trickier for me to explain, because while they will technically be present, I also want to stress they are not by any means going to be the end-all-be-all of what a character is a capable of. In fact I have no intention of implementing any strict rules regarding numerical power levels. Even though there will be people with Scouters who will read power levels from your characters, those numbers aren't really going to be all that meaningful. Much like the show, your power levels are going to be rising and falling based on your control of Ki among other factors, so they will quickly lose their relevance anyway.
4. The Dragon Balls themselves. Honestly, I'm considering the possibility of not including them at all. If nothing else, this will create a much more intense feeling of stakes since death would now be much more of a permanent fate and thus carry more significant weight to it. This point isn't set in stone, though, so if anyone feels we should include the Balls then feel free to say as much. I'll probably base my decision on what the general consensus ends up being.
5. Sagas and Arcs. Yep, we'll be using the structure of telling the story over a series of Arcs and Sagas - yes there will be a difference. Arcs will be shorter and sometimes more fillery, while Sagas will be longer and more plot relevant. I've already got a decent idea what the first two will be (The first being an Arc, the second being a Saga) and possibly a third though it will be delayed until later on. But feel absolutely free to suggest ideas for Arcs and/or Sagas. They can be used for exploring characters' personalities and backgrounds and be the platforms from which their character arcs can launch from or progress to. In other words, I very much want them to be just as character driven as they are sweeping and epic.
With those points in mind, the opening Arc will, as tradition dictates, be about Saiyans arriving on Earth - though not for the reasons you might be thinking of. For you see, though Planet Vegeta and its King have indeed been killed off, from there is where things will be completely different. For one thing, the Saiyan King left behind not one but two sons, and the older of the two wants nothing more than to kill his younger brother so that there is no one to threaten his claim to being the new Saiyan King. He sends out the few survivors he managed to gather to find a new planet for the Saiyans to take over, and in the process hunt down the younger brother and kill him. Said brother just so happens to be on Earth, having landed there 5 years ago and has been living there among the humans in a self-imposed exile. And I think I'll leave it there for now, wouldn't want to give away everything right off the bat.