The success of Medium has proven that lowering the barrier to write content is extremely valuable. If you're asking people to "work for free" then it should be as easy as possible and not feel like an errand. When you're inspired to write something, you just want to write it and not have the computer get in your way, or else you'll understandably give up. Wikipedia also proved this a couple decades ago.

Also rolling your own wiki is beyond stupid in this day and age. Just import all the MDN articles to MediaWiki. Making a script for this is a one-person weekend project. As I understand it though, Mozilla owns the copyright to all the content and they might shut you down for doing so.