How about the RAM though, games running on the 32x are still limited by it's 256k of SDRAM, right? You wouldn't be able to use the work RAM in the Genesis or CD. (except for stuff on the Genesis video layer?) Or could you use that RAM for other work as well, like tasks that you move over to the Genesis or CD processors. (ie could the 68k on the CD or Genesis be used to handle game logic and AI working in their own RAM or otherwise?)
This has also been bothering me, the 32x SH2's are on a shared 16-bit bus, but is this bus also shared with the 68k?
BTW, Chilly Willy, a while ago you mentioned you were looking into the CD ASIC's polygon rendering capabilities: