no sorry, once it takes over, it is not compatible to use two different processors, especially when they don't work on the same instruction level. The only way you can use dual processors, is when they both are the same type. There is no system on it that can handle which instuctions go to the CPU that supports a feature, while it doesn't send the same instruction to one that doesn't support a feature.

In anyway, you are stuck as soon as the G3 kicks in, it dissables the processor at hardware level and takes control of the bus. You would have to redesign the north bridge COMPLETELY and probably is not possible on the Mac Systems

The Lisa is the ONLY one I know of that can do that. But it uses the 6502 Chip for the boot and then hands it over to the 68k CPU