Since there's little point (other than nostalgia) of constructing a
machine with a genuine MC68000 CPU today and using the 68K-based
Coldfire MCUs is just too easy, why not implement your own CPU design
in an FPGA?
That would be fun and you'd learn something too.
Cheers,
Chuck
P.S. I built both NS PACE and GI CP1600 CPU boards to plug into an
S100 bus on my own time out of curiosity, but couldn't think of
anything to do with them, so they got recycled for other projects
after a few years.