this was really fun! I would love to see it fixed up and improved upon in the future. maybe even a full version if that's something you have the time for?
Along with the stuff you've mentioned as planned, I'd like to see some different types of notes. Maybe ones that fall slower so you have to pay attention to it's position while falling. (maybe a variation of this could move back and fourth as well, like a leaf) and maybe a note that has to bounce more than once (small bounce before being launched offscreen) and plays 2+ notes.
anyways, it's a very unique idea for a rhythm game. These are the type of projects that make me love game jams!