Most of the nuts came out with minimal force, but the last one just spins in place. I tried rubber gloves, painter's tape, and duct tape to get a better grip. I'd rather not cut a slot in the domed nut if there's another good strategy.
The rest of the restoration underway:
Super glue a socket to it, use a ratchet to remove it after the glue dries, then dissolve the glue away with acetone. If you need to you can glue a socket to the other side too to counteract the force of trying to loosen the bolt.
Super glue is super brittle. Will fail at the first bit of force
two-part clear epoxy will give a better hold and still dissolve with acetone