I'm not sure this would work well for the user, simply because you're distributing a limited number of jobs to a large number of developers. Even if you cap at 150, and only 20% of those are Pythonistas, that's still 30 people after the same job.

And frankly, most advertised freelance jobs are bottom feeders who just want cheap and fast. With this type of service, there's no big incentive for the service to avoid listing those jobs.

I'd much rather the placement service take a percentage, say 10 or 15% of the total. Then, the incentives are lined up right. They'll look for the highest paying jobs, avoid bottom feeders, and they'll be sure to give the job to the best performer in whatever sub-specialty area (say Python desktop apps).