I rather like disscusions like these, but I do have to point out that I can really see any future for this.
68k is not going to get any new hardware*... So the C64 and P96 systems support everything that is available. Both are basically compatible... Solid and in use... This idea is just reinventing the wheel without any tangible benefits.
*I really can't see any PCI-E boards for the Amiga being either comercially or technically viable...
There could be some merit in porting AROS's gallium gfx thing to MOS and AOS4... maybe?