There are already people that do that. They are called moderators, super moderators, admins...
This is a good idea in spirit but having randoms investigate stuff and making (mistaken) false accusations, doing payback punishments, etc is going to make this a nightmare. Rebuilding is nice, but if one of the re-builders "accidentally" griefs the shit out of stuff, it will be a headache. Meanwhile admins can roll back any griefs much more easily.
Perhaps you could make an adventure club, building club, cheese club, even a club to help people get their villages up to the level that they can be protected. Anything that doesn't involve doing the work admins do already.