[Using Sakai] MediaWiki - Grading and Rating

[csev]

I am doing some planning for a course I am planning to teach in Winter 2011 that will have a very large collaborative writing aspect to it.  

My first approach is to stand up an instance of MediaWiki and then use Sakai's IMS Basic Learning Tools Interoperability to plug MediaWiki into Sakai in each of the discussion section sites for my course.  The IMS LTI part is pretty simple and I mostly have that working in Sakai and MediaWiki already.

My question is how hackable is MediaWiki?  Are there MediaWiki plugins for things like grading or peer-rating of pages?   

http://www.mediawiki.org/wiki/Extension:Contribution_Scores

I am really looking for some guidance on teaching practice and experience around this.   The course will be a relative large class with 200 students in 2.5 hours of lecture per week and  1.5 hours of 20-student discussion sections per week.

/Chuck