Basically, you lack the only interesting thing which people actually play platformers for. All these technical stuff you've listed can be done rather quickly compared to the interesting game levels. Levels need a lot of thought, work and polish, also they tend to spawn features when some idea cannot be expressed by existing components. So if you don't have the levels, you don't have the game.
Summing up, you're basically going to publish a specialized game engine and ask people to make your game for you in return for a small fee while forbidding them to use this engine for anything but your own idea. Capitalism, ho! I've never seen it's done, considering how hard it would be to make a consistent game out of levels made by many different people. Just remember how nicely levels were themed in "World of Goo" versus list of abrupt challenges in "N".
If you don't mind these things, I guess it could work in theory, lets consider criteria for the best case:
- Community around your soon-to-be-game is large, so percent of creative people with nothing to do is high.
- Your concept and engine are heavenly good and/or money share is really tempting and/or it's otherwise attractive, so said people will want to become involved. Chances are, if you have troubles using your concept after the first level, it would be difficult for others to use it as well.
- It's would be frustrating for a community member to create a level only to find out that it won't be inserted into a game. You'll need to make this custom levels playable one way or another, or invent some other form of compensation for wasted time.
- You will spend a lot of time by helping lots of people with your toolset.
- You will spend a lot of time by sending feedback and doing overall community management, since you will receive lots of low and mediocre quality levels.
All points considered, it might be best to employ a "level-driven development" (think of possible cool applications of game mechanics, then build levels around them) or find yourself a level designer to do it for you. Also if your concept is good, it will be stolen regardless of what you do. Don't worry about it, real value lies not in a concept but in what you do with it.