If I were the one taking the project I would make an exchange for bitcoin and altcoins and give the option to sell credits.
System: 1 Credit == 1$
But the catch is that the company will make that credits only usable a whole month after purchase. This means that in the Terms of Service it should say that the time for the credits to be valid are so that the users can perform any chargeback if they don't see fit, and as protection so that if it is a stolen card, the rightful owner haves plenty of time to perform a chargeback too.
Alongside a secondary method of authentication could speed up this process via phone as an example.
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