When I was a teller, we were only allowed to keep $15k total at the window. Unless you get the vault teller, which is $45k. There are several different traps that are triggered by the teller if they get robbed. Exploding dye packs, several different silent alarms, etc. One time I set off a silent alarm on accident and the security company was on the phone in less than 5 seconds.

Definitely not advisable.