One more thought on this: Making a nice wiki doesn’t actually seem like that big of an undertaking. You summed up pretty well what we’re looking for:
a wiki is something that primarily displays structured information, that may be easily edited (either by everyone or by a set of registered users).
The things I particularly like about Discourse are the nice editor, the solid account system, with things like badges and trust levels, and the modern styling.
If that’s all it is… man, we should be able to write something like that pretty easily.