>199645For a minimal thing, I'd like to have SMB1 underground levels pallete swap the enemies and end level castle. A more major thing I'd like would be a way to have end level bosses that need to be beaten to get past, which could be done by either implementing wands and ball thingies, or just letting them drop keys.
One thing I've tried in a level I haven't published yet is having a regular SMB1 bowser, except the fight starts by dropping on a p-switch, and a wall of coins is placed to block you until it runs out. This turns out to be more difficult and itneresting to me than I expected, but it also means the o-switch music plays the entire fight since not even putting a sound effect directly on the p-switch overrides its music.