Uhm... two point.

In VT and NH it isn't illegal unless you intend to make a hasty withdrawal. I can't comment on other jurisdictions, as those are the only ones I'm cleared to carry in.

Second, if hostages are taken, SOP is you will be frisked when released through negotiation or more active intervention. If they find it, there will the assumption that you were a back up shooter and held as an accomplice until the charges are dropped or you make bail (good luck). I'd rather get the slap on the wrist (if any) and a cleaning bill from the bank than go through the repercussions of the plan you just described.