Well, my 1st assembler was IBM mumble... goto Computer History Museum to see a 1401 running; it had BCD representation (before ASCII), and variable-length fields for data, with the length being noted with a 'word mark' -- so you could add two 6,000 digit numbers with a single instruction.

Arm v8 seems to have fixed some of the arm v7 cruft -- what do YOU not like about arm?

My 2nd favorite is Z80 -- that also had 'automatic' move-a-string instruction (LDIR / LDDR). 8051 is OK. Z8 is OK. And MSP-430 is pdp-11esque.