Good job Geoff, however (And sorry to the easily offended) as far as the Video shows, it seems to be more of a major update to the platformer than a new creator. However I have some suggestions to make it better.
1. Make it a platformer RPG, good idea and also a unique way to aproach it, also a RPG was wanted.
2. The ability to use a Physics Maker style tool to make custom content, and the ability to imput raw code and assets for the advanced.
3. Turn it into a Tactics game, think of a 2D RTS, let still keep it centered around a central (But optional) Hero.
4. (The Best) Start with what it was planned as and then add in 1&3 as different game-modes (Shooter Ship & Robo) and then add in the Custom Content creator in a update.
Anyway nice job and best of luck to you on launch!
Tally-ho!