I like this idea, but someone else had already this idea (I think the webpage had an "X" in its name, but I can't find the link...). As far as I remember, the page wasn't like a wiki, but the admin put the content on the page - and it wasn't such a good resource, as it could have been.
So, do it - I'd like to see a true house rules section like "Dodge gives always a +1 to AC". A lot of things float in ENWorld around and if you don't bookmark the link, things get lost - and it happened already several times to me, especially, because I can't search.