This website is well organized. It was a good idea to build the manual, the FAQ, and other parts of the website in a wiki. However, I propose that instead of a single wiki, the website would be better served by multiple wikis. Specifically, I suggest one wiki for administration and development and three wikis for the game manuals 2.2, 2.3, and 2.4.
Organizing the documentation by version is a cleaner approach than organizing it by topic and addressing version differences on each page. If that argument isn't persuasive, consider that documentation is subject to the same revision control issues as source code, and it just makes sense to create a branch for each version.
MediaWiki has the capability to host multiple wikis with a single user base. If the website administrator would like to pursue my multiple-wiki suggestion and wants help with the MediaWiki configuration, just let me know.
-TC