You get an A+ for convenience, but selling an irrevocable currency for revocable credit is fundamentally a bad idea.
... or, in other words: have you thought about what will happen when somebody buys a bunch of bitcoins from you and then disputes the charge on their credit card?Or worse: buys a bunch from you, turns around and sells them to you. Waits a day. Does it again.
And then disputes all the charges at the end of the month...