I spoke to Joe who said the idea of making rear mud flaps was worthy of some investigation.
While the 10a/Rubicon X front and rear bumpers are off road, plenty of owners use the front MOPAR mud flaps which hang off the fender for daily driving to keep the grit off the doors / rear fenders.
Nobody is making mud flaps for the rear bumper it seems. I think it's a good idea to offer these if possible as it'll offer a little protection to those behind you and/or what you are towing.
I'd suggest sticking to the MOPAR style of molded and fixed in place so there would be a matching rear set to MOPAR's front, for those that like this type/style of mud flap, or even a complete front/rear offering.
Thanks for your consideration Maximus-3.