But the successful bad actors are more noticeable because they are near the top of the search while those you have to unpunish are hard to find.

Even if they can easily find them I think the real reason they want to stay away from it is that having such a tool would open a can of worms on the search neutrality side of things. (i.e. we know Google+ is a good actor we should remove link out penalties, we know are largest advertising client is generally a good actor, we should remove penalties from their site). Even if google wasn't tempted to misuse the tool you can easily see it generating a bunch of lawsuits form bad or unlucky actors accusing google of favoritism.