Banks use tools as a store of value by holding some assets in reserves, for various economic benefits. Although, adopting Bitcoin in such capacity, would have it's pros and cons. Obviously like controlling inflationary trends, and even help stabilize the volatility of Bitcoin to its users, and conversely such volatility could also alter the stability of a banks statement of financial position. All these could add up to a more stable global economy. Surely banks have started to think of such prospect
Banks reserve various assets to balance the risk. Due to volatility, they might not consider reserving Bitcoin against users' funds. But they might add Bitcoin to their own portfolio, like some other institutions that reserve Bitcoin. It does mean that from their revenue some of the part would be safely reserved. So they won't have problems even during the market dump. Because the reserve isn't against the value of the users' funds.
However, I am not against reserving Bitcoin by the bank. Just wondering about risk management during the dump. If the reserve is executed by the government directly, then it's positive for the country. Even if a dump happens, it will definitely recover and create a new high. Banks would need to develop something before reserving Bitcoin to reduce the risk.