[setishock]

Not sure about that but it's an interesting idea. However if you want to see what kind of job they're doing and not let them run amok, go in to the mods settings and set to just let them "soft delete". That changes the moderated post or thread to visible only to mods and admins. You have a couple of icons that appear that let you view the post/thread and manage it.
Going that route keeps the final decision to restore or hard delete at the top of the management chain.
Other than that setting the edited by to on and jamming the time down to 1 second for mods will show you if a post/thread has been altered. I think, not sure, there is a way to keep the original so it can be restored if need be.

On a personal note. Having to get permission to moderate will slow down responses to spam attacks or flame wars that break out from time to time. Mods need to be Johnny on the spot to stave off those sort of events. If you don't trust their judgment then they don't need to be mods. Finding mods you can trust is a long hard road. I looked at other forums I hang my hat at for a good while before asking a couple of members if they would like to mod my place. The one that did respond is doing a bang-up job and I leave the place in his hands and sleep like I'm dead.
Keep the controls tight but try not to tie their hands.