Whoever is going to implement this: There exists a wiki which seems to be near optimally suited to build this: The SmallestFederatedWiki how it looks source on github wired post about it. It is decentralized, simple to deploy and most importantly easy to extend via scripting plugins. You should be able to easily add voting and a tree/graph view.

(I'm not affiliated with this, just toyed around with it. The code is readable and indeed small)