If we exclude addressing mode then I think there are less than 26 instructions. Our mnemonic format was one letter (verb/op), one for source (a,b,c,d,e,h,l,w,x,y) and one for destination. I dont recall the letter for immediate, probably i but MIA for move immediate to a doesnt ring a bell for me. :-)
As a pragmatic manner, I don't regard having the register and/or addressing mode encoded into the opcode as a separate opcode.
Emulating a modern 64 bit processor would be a major chunk of work, but the old 8 bit ones are simple.