Here your basic problem would be to get sufficient number of jobs for providers to signup. That'll be hard given elance and others already do that and they've already taken care of one-click payments across the globe). Infact most of the devs on elance are already from 3rd world countries, and the first world people find it hard to compete with lower pricing.
Infact going the other way might be lucrative(hypothesis!), i.e. cater to a projects in niche domains, or setting a lower limit on the project/hourly price. This way you're not competing on price, and focusing on quality. There's a dearth of those marketplaces right now.
Maybe you should focus on the opposite niche: European freelancers, American freelancers, Australian freelancers...