I fulfilled another request, this time made by Sweetdude. He though it would not be vanilla enough so he erased the request, but I got enough interested on it so ended up doing it. I won't be submitting this one to the patches section for now, though, since it's still not fully compatible with SA-1 and it still has some issues, but everybody who wants it can download it here:
Pokeball Effect (beta)
This patch makes it so an sprite touched by Mario's fireballs gets "stored" and it can be "released" when Mario fires away another fireball that touches a solid block. It should be used alongside the uberasm (since the uberasm sets the freeRAM flag necessary for it to work, so make sure to only use the uberasm code in all levels you want the powerup to be active).