One of the critical, game-breaking elements of this project is getting a payment API integrated into our code that works the way we want. Stripe, PayPal, Braintree, and a handful of the other usual suspects are in consideration right now, each with their own merits, and probably none with exactly the perfect combination of features that we'd want.
Some of these limitations are those we ourselves bring to the table: we're a UK based company, and this limits many of the things we're able to do with a system like Stripe. It's frustrating, but there's no getting around it, and particularly disappointing given that Stripe has so many other features we'd want to take advantage of.
We're jugging a few options here, hope to have an answer by end of the day's coding. PayPal, despite some juggling about getting accounts are cards set up, may well prove the most viable option here, provided that we can solve the issue of verifying images as fast as credit card details.