It's not a co-option. The banks are using Bitcoin as it is meant to be used: as money. Money is a token that substitutes a real good in any trade.
Religions have tried to crack down on things like usury because it's the "dark side" of money. If you're going to substitute a good for a token, then any token will do. Even a token that doesn't exist. This is the true nature of money and it's "exploitation" as fractional and fiat money are actually intrinsic features of money.
If you use Bitcoin as a tool to replace goods in trade, then you open it up to that path of good and proper usage. Fractional reserves, derivatives, debt instruments. They're all fair play because they're all forms of money that people can use to replace goods in trade.
The genius move that the money masters discovered is replacing both sides of any trade with money, and just trading tokens back and forth. There's no "good money" and "bad money" except in fairy tales told by economists.
