Kale and JD have a good point in this discussion because they are the current SNES driver developers, and they are doing lots of improvements to it, spending their spare time to try to fix the whole thing instead of saying what should be done from today forward.
For what it's worth, the SuperFX, etc. cores were all a few days' work, tops. Including me in the list of current SNES driver developers is giving me too much credit, I think.