I am not an major expert on these thing, but i can manage designing parts etc because i am engineer.
You could always use custom made hubs, and have either porsche rotor or wilwood rotor/hub assembly.
I plan to use wilwood 330x28 rotor, hat and custom type hub for beetle bearings, allready have designed the basic hub.
Caliper adapter should not be a problem at rear if you use monobloc caliper, easy to design bracket. Sebro has porsche rotor dimensions, so you can check that if any other porsche rear rotor fits instead of stock turbo 299x24 rotor.
Here is an old version of rotor/hub/caliper assembly with 310x20,6 rotor
