The problem with not having an exchange is that I would have to pay trading fees to an exchange in order to have Bitcoins to sell. This would be like Bitinstants method, and I do not want to charge 4 percent in order for people to get their coins. If I have my own exchange I will not be charged any trading fees, thus I will be able to sell coins at a much lower rate.
I disagree with this analysis on a couple of levels:
1. Exchange fees on, say, mtgox are half a percent. When you start doing significant volume, it goes down to a quarter percent. There's room for that in your margins. And I'm betting it's insignificant in comparison to whatever the credit card company is charging you.
2. Even if you had to go to 4% (which you do, due to credit card fees, right?), customers would still buy from your company. Just ask Bitinstant. Or better yet, convince some wealthy bitcoin investors that you really can do it, and watch the investment dollars pour in.
3. Having your own exchange would probably not even save you/your customers anything, especially if the credit card thing works out. Dollars would fly into your exchange, and drive the price up relative to mtgox and other exchanges. Arbitrageurs would step in but there's a limit to how tightly they can keep markets in line, and 4% is not out of the question (ever look at the price differential between btc-e and mtgox?). Because of the higher price on your exchange (and likely wider spreads, at least for the first year+ unless you magically steal a huge chunk of mtgox's liquidity out of the gate), customers would end up paying 4%+ over the mtgox price anyway to buy bitcoins. This is what happened with bitfloor, because they provided an easier/faster way for US folks to get cash onto the exchange but didn't have mega gox liquidity.
I think the real challenge here is to get started with the credit card thing, demonstrate that it can be done profitably, securely, and legally. At that point you could probably sell your company to Bitinstant for a handsome sum. Though you might prefer to keep making money hand over fist for yourself. And hey, maybe then you can look for a strategic partner with an exchange to shave off another .3 percent for the benefit of your customers (or profit margins).
I think this is currently the state of the art for buying bitcoins with a credit card:
http://howdoyoubuybitcoins.com/with/credit-card/