Couldn't you do federated wikis using IndieWeb building blocks? So each wiki entry is an h-entry say. And if I want to copy to my wiki from your wiki, I have an action that parses your wiki entry microformats, and posts the copy to my wiki via micropub, ready for me to edit. And maybe sends a webmention to your wiki perhaps, to let it know where other copies exist that have been taken.
Not sure if that's 100% the idea behind say FedWiki - what does it actually mean by federation?
Isn't the web just one big federated wiki?
And maybe, just maybe, it's not so bad to have a wiki in a central place. The indieweb wiki is, for example.