Wow, cud you have found a tougher one to work with?
I notice the number wheel has shrunk the most, and taken the brown wheel with it. to flatten that, will prob take the outer ring of rivets out of the number ring. not sure, but looks like they are almost out anyway.
You will need to make a jig to lay that on, and one to lay on top as any edge will imprint in the number wheel.
You may be able to remove the rivets, flatten, then drill and re rivet ? then you cud press the number wheel between two flat heavys, that would ix the number wheel.
The brown one would be more forgiving once separated.
Also, the brown one wud take more heat to flatten...if it did.
the number wheel cud be scanned and reproduced pretty easy.

Pinball Rescue has made a few animation wheels but nothing yet for Sunshine. They seem pretty receptive to requests from what I understand. You should check to se if they could do a run.

http://www.pinballrescue.net/Animation%20Plastics.html

Pre-1960 plastics basically don't flatten. The plastic material changed right around then and will flatten with heat. The older style plastics tend to curl up and become brittle (and don't budge with heat), while the newer style develop more of a 'wave' to them. Those are the ones that will flatten. 1960 seems to be the crossover point, so I would be doubtful of any luck with that one, since it appears to have shrunk (and taken the disc with it).

A new one could probably be fabricated with a piece of Lexan and some waterslide decals, and the wiper disc may flatten out, since it's being held hostage by the shrunk plastic. The rivets could be replaced with small bolts/nuts if didn't want to mess with rivets.