I know, I know... extreme wishful thinking.
Be careful what you wish for :-)
If the PPC has access to the address space of the host Amiga, it can access the custom chips under OS4 just as it can do that when running OS4 on a CyberStorm or Blizzard (before somebody adds a "sarcastic" comment: It can access the custom chips ;-)).
However, using the 68k CPU is out of question. There are too many problems involved when running the real 68k since it's not cache coherent. The JIT will emulate a 68k CPU at acceptable speed. I know the compatibility is still a problem, but it's progressing.