Ideal in what regard? Easy to code for humans or generate for compilers? Code size or decoding simlicity? Parallelism or cache friendliness? Energy efficiency o

Ideal in what regard? Easy to code for humans or generate for compilers? Code size or decoding simlicity? Parallelism or cache friendliness? Energy efficiency or low cpi? Flexibility? Future-proofness or backward compatibility? In theory you only need one instruction (subleq), everything else is a highly narrow optimization attempt.