Have you considered giving a bit more structure to the "Idea" submission? Maybe just split out basic questions like "What problem is this solving?", "Who is this for?", etc. into separate fields. Might give it a bit more organization and would potentially allow users to categorize/search based on certain criteria.
One assumption that would need to be tested is whether people will take the time to review ideas. And the other is whether people would be willing to disclose their ideas so publicly. I think you can find better quotes/articles to help convince people to disclose their ideas. Here's an excerpt from Paul Graham's How to Start a Startup essay you may want to use (PG has some more good quotes on the same topic in some other essays):
"An idea for a startup, however, is only a beginning. A lot of would-be startup founders think the key to the whole process is the initial idea, and from that point all you have to do is execute. Venture capitalists know better. If you go to VC firms with a brilliant idea that you'll tell them about if they sign a nondisclosure agreement, most will tell you to get lost. That shows how much a mere idea is worth. The market price is less than the inconvenience of signing an NDA.
Another sign of how little the initial idea is worth is the number of startups that change their plan en route. Microsoft's original plan was to make money selling programming languages, of all things. Their current business model didn't occur to them until IBM dropped it in their lap five years later.
Ideas for startups are worth something, certainly, but the trouble is, they're not transferrable. They're not something you could hand to someone else to execute. Their value is mainly as starting points: as questions for the people who had them to continue thinking about."