Anything in particular that you like about the 6502?
https://en.wikipedia.org/wiki/SWEET16
or the truly atrocious
https://en.wikipedia.org/wiki/UCSD_Pascal
which was one reason a generation of programmers hated PASCAL with a passion and declared you could pry BASIC from our cold dead hands.
Myself I'd want to hollow it out and put something based on
https://en.wikipedia.org/wiki/Zilog_eZ80
because it is way faster, has a bigger address space, and has wider registers so you can do pointer math over that bigger address space unlike this turkey
https://en.wikipedia.org/wiki/WDC_65C816
A lot of people enjoyed writing assembly for the 6502 back in the day though.
And the Constellation OS from Corvus Systems.
C compilers on Z80, at least on Spectrums were really lousy in terms of code generation, plus the whole dev experience unless on a +3 A with drive, those kind of machines were designed for a BASIC interpreter + Assembly.
I find it fascinating how these 70s/80s microprocessors still keep getting pushed with backward-compatible updates. (Most notably, x86-64.)