I don't find any problem with using MediaWiki. You're talking about problems with having open content, and that's not really the debate here.
In this moderation would be given to people who have proven they understand the topic material at hand in the forums, and if a forum thread comes up which has good material, that forum thread can be converted into a wiki post.
If we found that moderation of new users was too hard, and the site was being filled with bullshit, then we could restrict the site to being invited by an approved user. This way the network could expand, but only through someone who is trusted letting you in.
Also we would place an emphasis that this wiki is not a place for discussion of anarcho-capitalism, it is a place for providing a proof for anarcho-capitalism. In this way, if someone wants to argue some point, then they need to go to the forums. If someone doesn't meet those guidelines, then their subject can be edited/removed, and if they persist they are moved.
I have had a lot of experience administering and using MediaWiki, and the only trouble we might have is integrating it in with the rest of the mises site so it all looks the same.
My vision for the site is to have it into 2 types of material, theory and scenarios. Under theory all of the different theories are presented with examples and links to theories it relies on and criticisims. Under scenario's there are cases and examples of what *might* happen in an anarcho-capitalist system, which draws on theory from the theory section. We can setup categories to help divide this and make browsing easier. This should become a resource such that, when we are arguing with someone online or in real life, we can send them to a specific link, which provides a scenario for them, backs it up with theory, and allows them to slowly iterate through the site, piece by piece, slowly understanding anarcho-capitalism. This is the goal of this service.