Very promising, I'm really looking forward to seeing how this comes along. Very slick interface with a really nice idea behind it!
Right now, I think the biggest thing this needs is an in-software map/scene editor.
Having the ability to call upon a tileset for map data, rather than having every map be a separate image, would greatly reduce the final size of games created, and is the way that most Gameboy games worked back on original hardware.
Keep up the great work!