Implement per project or core/module permissions

How are we able to split approvals between core and modules? Core translation have rules that need to be followed, but we haven't cared sooo much about the rest in past and allowed everyone to commit translations to CVS. As I know - if someone like to maintain a module translation we are not able to block him from approving core strings... how should be keep quality in this case? On the other side - approvers may not like to work on translations of unpopular modules...