The volatility of the bitcoin is due to speculations and illiquidity. That doesn't mean it doesn't have an intrinsic value. Like the dollar (which isn't worth a dollar from one moment to the next by the way; see inflation) bitcoin is a fiat currency who's value is decide by market efficiency (a fancy way of saying we say its worth what its worth, tautological, I know). Since a bitcoin can be used to buy goods and services direclty, it isn't dependent on any other fiat currency, dollars, euros, or tulips. It can be converted into those other currencies and commodities, and since those other currency and commodities are also convertible into eachnother, in an efficient market the the conversation factors would all be reconcilable. We don't live in an efficient market, so they're are discrepancies in the conversion factors. Your business model is simply arbitrage is taking advantage of the discrepancies, aka skimming off the top - which debases the currency. See superman III for more information.

I wish you luck with your venture, it's not the bank for me though, as its not really any different than the royal bank of-JP-citi-SBC-ice-Scotland, inc