AROS on ARM is the best option, with a 68k emulator for native app compatibility (hopefully still calling the native AROS libs, like OS4's Petunia emulator).
Petunia (OS4) or Trance (in MorphOS) is more of a binary translator/recompiler than it is a emulator/simulator; it basically recompile the 68k bytestream into native PPC code. This makes sense on a big endian HW architecture like PPC, because it makes it possible to mix "68k code" with PPC code in the same environment and run old and new programs (and OS components as well, like ARexx for examples) in the same environment as they were no different to each other. In fact they *aren't* different, both 68k and PPC apps are all de-facto PPC native at runtime, being scheduled by the same scheduler, sharing the same memory and system resources, etc. In this way, both MorphOS and OS4 *is* the native Amiga environment, where both new and old applications runs side by side, but on a different HW platform.
This isn't really possible on a little endian platform though, and AROS has a different approach where UAE is used to emulate a complete Amiga machine (with 68k CPU, custom chips and the whole shebang). The upside of this is an improved compatibility with very old SW and/or HW hitting applications, but the downside (compared to the MorphOS/OS4 approach) is that the Amiga apps runs "sandboxed" inside this emulated Amiga, and the AROS native ARM/x86 apps runs outside this box under AROS.
An FPGA for native hardware compatibility is a nice thought, but would turn the hardware from cheap commodity into bespoke expensive. So a perfect match for this community.
A terrible idea if you ask me. There are mainly two groups of Amiga users today, those who are here for the "classic", who are more of retro fans today, and those who are here for "NG", which is more about evolution than retro. The retro people use real Amigas, or emulators, or "new classic" HW like Minimig.
A product like you are talking about would not suit the retro fans, since they are more interested in "the real deal" and 100% compatibility (and like it or not, new HW compromises backwards compatibility). And the "NG" fans will feel the platform is being held back by 20 year old museum level technology. So it would be stuck in the middle, not really satisfying any of the groups.
IMHO of course!
