I went and found my code, with a side trip into being able to "unzoo" the archive!

Yes, I agree. I also used SI as the PC so I could use "lodsb" (cute HN name BTW) and "lodsw" for 2 byte args.

My register use was

   286   Z80
   ---   ---
   BX    HL
   CX    BC
   DX    DE
   DI    A
   SI    PC

When emulating the DD, FD and CB prefixes I pre-loaded BP with either IX+d, IY+d (IX, IY were stored in memory) or BX and jumping to common code.

Basic structure was like

  OP_00:
     XOR    AH,AH
     LODSB
     SHL    AX,1
     MOV    BP,AX
     JMP    CS:OP_table[BP]

For OP_02 - "LD (BC),A" I used,

  OP_02:
     XCHG   CX,DI
     MOV    [DI], CL
     XCHG   CX,DI
     JMP    OP_00

I did see some opportunities for additional code-golf. Also noticed that EX AF,AF' did not properly exchange the flags (so that will need to get fixed!).

I was mostly only running m80, l80 and mload.