For the sake of nostalgia, it would be cool to be able to run MOS or OS4.0 on classic hardware, through CPU accelerators such as BPPC, CSPPC, and especially SharkPPC (assuming it wasn't vapor), but designing something other than add-ons (e.g. PCI busboards and similar stuff) for existing C= made motherboards, let alone new Amiga systems that have the custom native chipset upgraded to today's standards, would be nothing else than financial suicide for the company or person that attempts it. It probably would be possible in theory, but there's absolutely no reason WHY anyone should invest millions and millions of $$$ to do it.
Pegasos and AOne have been optimised perfectly as far as realistically creating the Amiga feel as much as it is possible at this point in a new piece of hardware, for a reasonable price, and being architecturally different than PeeCees but not to the extreme like the custom chipset of the classics was, so that cost of manufacturing wouldn't be over the top, which is important if we wanna be able to easily use the existing standards in expansion hardware.