Question

Ok, here's an idea: If the blocked user's user page is protected at the mod level, their block can only be changed by a mod. It's a hack, but it's pretty easy to implement.

Dammit, there's no hook for unblocking, so I can prevent changing blocks, but not unblocking. I've got to go now, I'll get back to this later.

Well shit, I was hoping unblock was treated like a change block....

Editing MW so that unblock = change block to 0 would solve this, I guess, but may be way too much hassle.

We don't want to edit MW, maintaining a patch is too much work.

Do it properly and you can upstream your patch.

Been there, done that, getting a simple patch for an actual bug upstreamed takes forever, can't be bothered.