The one thing I really want to see in Sonny 3 is the ability to use any and all abilities in the game through some method or another. I don't care how many hoops I need to jump through to get both Tick Tock and Blade Metal (or whatever Felicity's 95% heal reduction move is) on the same guy, I just want to be able to do that (as well as all the other ridiculous combos out there). Sonny 1 did this in a way, but basically everything had the same moves anyways, so it wound up boring as a result.
Idea for the levelup tree: Have one tree with 8 branches (one per element) and arrange the elements in a manner that sets opposite elements across from each other and similar elements next to each other. The point is that the farther you go in one direction, the more limited you are in other directions (you can't be both pure fire and pure water, for example). I'll make a picture to illustrate this later.