I would try to become a customer so that I could access the bank during the day and check out the vault area. I would need to team up with someone who could disarm the security system…preferably with grenades. Then I would just go in with an explosive device and blow the door off the vault. I would try to muffle the explosion with something …preferably my ex.
Though I applaud your creative use of explosives….and ex-boyfriends…I’m not sure this one is very realistic…..Laughed my ass off though!