A huge problem is that MediaWiki is notoriously lacking in access
control features. Generally, the access modes are either "wide open" or
"exclusive membership" (and you have to hack PHP code to change modes).
We're down-rev a few major versions on the MediaWiki software so it is
entirely possible that they have improved some stuff. If only I had time
to upgrade. (To further exacerbate the problem, MediaWiki releases a new
major version ever quarter whether it makes sense or not, and it's all
documented in -- you guessed it -- Wiki format.)