Helium.com provides upfront payments outside Canada and there are no unusual tax requirements with them. You report your earnings as self-employed income (or you're supposed to) and the government of your area taxes you accordingly. And you'd be surprised at the English of my foreigners. A lot of areas actually have the majority of people able to speak English quite fluently.
Alright, here are some ideas. You should be able to sell complete rights, partial rights, or "rights for the site only and subject to removal." The last would let writers allow the site to post the work only on their site, but the writer could remove it from the site if they chose to do so. With the second option, Helium.com allows companies to contact them and purchase usage of an article. That is a nice feature. They also let projects appear that writers bid on. If they lose, the article simply because a site article that generates profit.
My personal issue with upfront payments is in relation to how it limits topic potential. If you can create a topic on politics that makes money while 95% of people can't, you deserve upfront payments. I'd say upfront payments should be "bonuses" in addition to page views. Once someone hits X amount of earnings with an article, they get an upfront payment.
Of course, some people just want to make some money quickly, but given that most sites pay monthly it's hardly that "quick" anyway. SEO tool would be neat, allowing links to their sites might be nice.