Force "submit for review" on update?

I'm trying to force all content to be submitted for review. That means that if a user updates an already published page, that the update would be pending until someone else approves it.

I don't see an option when looking at the wp's capabilities. Most role/cap plugins try to do too much and end up creating a mess. Any ideas?

I guess, a better question, is if there's a way to save a post as a revision, instead of updating it?