This is an interesting idea. I've been thinking along similar lines myself.
However, I'd like to have some FPGA between the x86 and the Amiga to translate and to handle SMP, so the Amiga thinks it sees a ridiculously fast single-core 68k chip rather than a multi-core x86.
This would involve some looking ahead and translating in parallel as the FPGA would be somewhat slower than the CPU.
