I've always wanted to write a tool like Game Maker that was built, itself, on game design principles. Make a level, get XP. Game mechanics that synergize give you combo points, that you can "spend" on a Mechanical-Turk-like marketplace to get people to contribute 5-10 minutes of work on your game, or playtest it. Every time an A/B-tested-metric you've inserted moves positively, you unlock new premade-resource-packs. Etc.

It's been done already! Has incredible graphics...