I had high hopes for this and was immediately turned off by #3. I still can't believe that their are developers who believe that design is just the pretty layer on top of their functioning infrastructure. It's not. That said, I wish there was a site that connected people with complementary skill sets around similar product ideas.
The idea is to connect someone who has created something technical and useful in concept with someone who can create a wonderful user experience out of it. These are not always the same people.
I agree with your idea (#3) but only as the reverse -- imagine a website of "ideas" and mockups waiting for people to implement them. I believe great apps start with design, not with a backend. (Of course you can write them in either order -- the point is to have considered and drafted a design before starting on the backend).