http://rpguide.wikidot.com/
It's bare at the moment, but it is made. It is set so that only site members can edit pages and site members must be approved via applications. I believe it's simply signing up through Wikidot, then hitting the Join button. After becoming a member, you can edit any page unless it is restricted to only admin/mods. Additionally, any revisions can be reverted unless deleted by an admin/mod.
Essentially, this will be a collaborative effort just like any other wikia, but I will be selective as to whom I allow to assist as they need to be knowledgeable and trustworthy, as well as productive.
Onto the second topic, I have yet to flesh out structure in terms of how I want the guide to be built, but I have plenty of ideas. The reason for this is that I did not want to design a site that just needed expert opinions tossed in. I do truly want it to be a collaborative effort not only for the increase to comprehensive quality but also as a symbolic gesture to what roleplay is. That said, I will discuss what I did have in mind.
As I said originally, I want the site to somewhat be a textbook and referent for roleplayers. All textbooks have chapters and are designed so that information adds to itself and becomes more complex as it goes along. This pattern is similar for almost all textbooks be them for Physics of Appreciation of Arts. With that in mind, I want to set aside information as core 'fact' that all theories we discuss will refer to and we will fit all models to be comprehensive of, then I want to discuss opinions, models, theories and the different styles of roleplay within a subtype and how they might bridge over and connect to different ones of a different subtype, or how there might be a pattern of sorts.
As you can see if you take into account just how many subtypes there are and the variety of different styles, this is definitely not an endeavor I can accomplish alone. No one can, really. The first step to this guide should be to set the ground rules and state the mission of the guide. You see that in the preface of almost every major textbook. This will not only lay the foundation for us as a team, but it will help the reader understand how the guide will work. After that, I would go on to set definitions that we design and agree on to define roleplay in such a manner that they will apply to all branches and subtypes. I would go so far as to try and make them so all-encompassing that they could technically describe roleplay such as LARP, tabletops, virtual RPG's and text-based adventure style roleplay. For instance, when I took on the title of mentor, I taught roleplay as such:
Roleplay - (verb) the act of simulating the thoughts, behavior and actions of a character to interact with other characters and a setting
In this case, the setting included the environment, society, culmination of plot-based events, etc. I made such known by setting a definition for what a setting is. Obviously, roleplay can be used synonymously with setting, thus I had to go through and create several different possible definitions for each word and if I referenced a definition within a definition I'd make sure that word had a superscript for reference.
All of these words will need defined multiple times and we may have to go back and edit them as we encounter new information and methods of thought. That should be part of the process.
As the 'chapters' would progress, we'll get more advanced definitions, sometimes create a definition of a word that is only applicable to a subtype. This is where the expert opinions in the field will come from. And, when it comes to an opinion that every just agrees is wrong, we'll omit it. Even though it isn't relevant to this guide, if you all voted against my stance on Elitism and social stratification within roleplay, I would forfeit it and move on. We might make a note of it somewhere that it's not a universal opinion. But, the point would just go on. Some people might drop the project in such a case, and if so, too bad. You can't make an omelette without cracking a few eggs.
After that, we can discuss and create pages for topics such as Character Concepts vs Character Sheets, what a Character Sheet is and should be, etc. I see dozens and dozens of splendid topics in the Roleplay Discussion Forum that we could format to our guide style. And, on that note, we would have to keep that in mind. Even if we have a thousand people cooperating, this is going to be a guide, not a rulebook.