A couple of potential stumbling blocks.
1. - The NRA is a non-profit. Not sure how that would work if they start a bank / venture capital / financial institution...etc
2. The feds control the banks through the SEC and the federal reserve and other Gov't institutions.
On the positive side....I do not believe the actions of the Gov't to sway banks away from certain types of businesses would hold up in court. If it did hold, imagine how easy it would be to buy stocks in one company and then cut off the money supply to all of their competitors. Remember, the liberals are all about regulation and oversite