I am kind of shocked that no one has utilized all those beautiful sprites that we have at our disposal, and created a Super Mario Metroidvania. It is perfect, you could start off small, eventually get large and gain the ability to bust bricks with your head, thus allowing you to reach areas that you could not before. The fire flower naturally gives you the ability to (gasp), melt ice, thus opening up new possibilities there. Of course by Super Mario 3 you had all sorts of costumes, and by World, the ability to ride in a cloud (as originally planned). So with all of this in mind, why has no one done this before; it could be done great like Monster World V and Wonder Boy 3 great if not better! In fact, why isn't this a part of Mario Maker? RPG elements and what have you? If I didn't have one unfinished game on hand as it is, I'd be half tempted to pick up a game creation engine and give it a stab.