Would it help much? A rogue pilot has the advantage of surprise. They get the first punch - and with a little luck and some practice, one punch is enough. Lock door, punch unsuspecting attendant in the face, pummel them unconscious before they recover.
Or, as I've posted elsewhere, don't even bother with a physical flight. In the US, where two people are required on the flight deck, all flight personnel are automatically eligible to be Federal Flight Deck Officers, meaning that after taking some amount of training they can carry firearms on the plane with them, and other flight officers/staff are prohibited from asking or knowing that they're carrying weapons. If pilots want to crash a plane, it's not going to be difficult for them to succeed.