IMO, the AWD computer-driven cars should NOT be in the same class as any RWD or FWD cars.
Heck, if it was up to me I'd have cars only running against cars with the same drive layout. The way each layout handles and performs is so different from one another that I think it would be more fair to make them perform against similar cars. I know I've seen a course that was pretty drastically favoring the FWD cars. Instead of them cleaning up the RWD/AWD cars, FWD would be running against FWD, RWD against RWD, etc.
I don't think engine layout would matter as much...
I know, I know, file that in the ever-growing "Things I don't like about SCCA classifications" list.