Tip: Switch palace switches normally disappear if you replay the level. However, if you insert them as direct Map16 and use the hex edit at $00EEB2 in the ROM map, you can replay the level without a problem.
Indeed, makes water levels a lot more enjoyable. The only thing I didn't like was the fact that the button is not configurable - I would have liked to maybe use Y instead of X. But IMO that's not a rejection reason, although if you submit an update that fixes that I'll accept it. Also made SA-1 compatible (i didn't test it with SA-1 though).