But, what would be destroyed here? A Phase5 board? So what, amazing there is a new replacement
The ultimatePPC is not a replacement for a phase 5 board & neither is any of the "new Amigas". If you want an AGA machine with a PPC board that will run all software, then you have no choice put to pay the inflated price of phase 5 boards.
If the ultimate ppc had a CPU with the full FPU then the price of Phase 5 boards would drop. I just can't see this becoming the must have accessory.
So in theory you could use a soft 68K on x86 as well. Provided it was cheap because of the CPU. With that speed endianness becomes a low issue.
I agree, as the PPC they chose isn't compatible with alot of existing PPC software and will have to emulate the older processors to be able to run all software then using an X86 would make a lot of sense to run 68k & PPC software. If you could make it act like a bridgeboard as well then that would be even better.
There is no reason why an Amiga needs to have a real 68k at all. When you plug in an accelerator board it disables the onboard processor, on the german a2000 you had to remove the onboard processor. You'll need software to boot the machine up, which would either be an emulator that runs Kickstart or it could be something new that just configured hardware and then booted from hard disk. A boot menu could then allow you to pick between running kickstart under emulation or booting linux or windows.