You do realize that mainstream Snes9x support MSU-1 now, right?
Also, MSU-1 is possible in real hardware as well, even with repro carts IIRC.
MSU-1 hacks are an incredible feat, I wish I knew how or where to start since I've been wanting to do one for EarthBound, I already have a full PCM pack ready to just shove in there, but the ASM code is missing.
All in all, MSU-1 is now becoming more accepted with more emulators supporting it as we advance, Snes9x being a prime example so we can get rid of the task-consuming bsnes to enjoy such a thing.
Also, latest versions of Snes9x through RetroArch also support MSU-1 as well, so that's yet another way to go for it, simply naming the tracks and everything with the same name as the base ROM and you are set.
With MSU-1 we can have PSX quality games in the inferior hardware, just look at qwertymodo's Chrono Trigger MSU-1 hack, he managed to even get the FMVs working for that game in the SNES.
You really seem to not take into consideration the amount of technical work that happens in behind the scenes for these and many other technical hacks which the casual player doesn't even care about, only hackers, like the mapper hacks for NES games.