Of course, with the FPGA based systems you're not necessarily restricted to a single processor core, though you'd need a very large FPGA for multiple M68K processors I imagine. But you could, in theory, create a universal Atari compatible, backwards compatible but looking forward.
Something possibly in a TT/Mega STE style case with built-in ethernet, 68000 and 68030 cores, full USB 2 High-Speed capability, HDMI output and able to run in ST(e)/TT and Falcon modes as well as its own.
However, the design work would be huge and I very much doubt you could get enough people to work upon it or order enough to make it viable financially or operationally.
The ZX Spectrum Next project is far less ambitious and builds upon previous designs and yet it's taken two years by a team of, I think, four and a big crowd funding campaign to get where it is today, and it's still not shipped (the final product) almost a year late, though a lot of this is due to the case.
I think the key lesson to learn is never under estimate the amount of work involved. Make a pessimistic estimate and double it.

Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.