The problem is, sales and marketing people generally don't have good ideas for startups. Because they're not masters of the medium, they don't know what's possible.
Rokhyakebe in your suggested model marketers will have the vision and not the craft and programmers will have the craft and not the vision.
How many people think designing software is as easy as designing a spork?
You're kind of proving my point here. Designing clothing is hard. Designing web apps are hard. You need to be good at each to be successful at each. You won't be good at either if all you have is a "business/marketing genius" with an idea.