And I can see this taking off. Obviously not fast because most of your potential customers wouldn't even know yet they need your services, but that should be able to slowly bootstrap. And I suppose once you would have built a strong team and gotten some notoriety, you would be able to bootstrap your technological edge into some concrete product.
Having said that, I still have some doubts, mainly because I think we are in a coding bubble, and the future belongs less to the programmers than to the engineers who will build the new space rockets or the technology to exploit green energies from example, while with the standardization of functional programming and the development of various libraries it will be easy for a non programmer to start creating software components that are currently requiring programmers (IMHO there will be less "pure" programmers and more "X's who can program" as you once said here on HN).
Nevertheless I wish you can succeed with your idea, even though I don't think I'll be able to work in your company as I am not a top programmer.
My end goal is for this to congeal into something like an open-allocation environment, but one that exists across companies to some extent. I feel like if we bring OA to the external market, we'll force the hands of employers who will have to improve conditions if they want to compete for talent. So, the trans-corporate open allocation (because each person carries an income that follows her whereever she goes) is the ultimate end goal. That may be completely insane, but isn't that what the open-source gift economy is-- trans-corporate collaboration?
Getting designers, marketers and domain experts will be hard. I grant you that. Strong designers and marketers I can spot; domain expertise I would not be able to tell, unless I had it myself and, of course, for most domains I won't. I think that to get a domain expert, you'd have to hire her into a company already formed through this process, because you're right that there's no way we can build up a competent selection process for every domain we might care about.