Since it's a little hard to adjust speed/jump height with the very limited amount of boots in the game, I feel like we need more boots (or at least more boot slots).
So far the only two boots that make a difference in speed/jump height are the Running shoes and Winged boots. What if we had more boots that, if they didn't vary in magnitude of speed/jump height, provide neat abilities? Like maybe the ability to walk on walls or wall jump on completely flat surfaces. Or even better yet, increase the player weight and press heavy switches that could not be pressed otherwise (I mean sure, the Iron Boots kinda fufills that role, but having a use for that bothersome weight would be interesting).
Maybe even shoes that allow the player to walk on the surface of water for a bit would be interesting.