Perhaps allow crats to desysop (requires a little developer work, but not too much), and leave it pretty much to their discretion, similar to how blocks are pretty much at admins discretion now.
Though unblocking is at other admins' discretion, and there's lots of back-and-forth on WP:ANI if an admin doesn't seem to have a feel for the spirit of the blocking policy. (Not to mention here.)
Yes, and it works quite well. Wheel warring is sufficiently frowned upon that admins don't go around undoing every block they disagree with, but when an admin makes a serious error in judgement, someone will undo it. I think the same principle for desysopings would work equally well (although may require a few more crats than we have at the moment).