I agree that it can be very frustrating with jumping in your vehicles. But the problem with locking from the inside is that everyone is gonna be doing that, and then PvP on an enemy vehicle will not be rewarding at all. If locked from the inside then you cannot get their vehicle nor loot the players gear. The vehicle becomes a moving Safe. Best way is to just play on a server where safezone griefing is a bannable offense. For every other location this may happen, well just look out I suppose. Number (2) and (3) suggestions I think are really bad suggestions. Not sure you can even do that in ArmA. I think the bottom line is just "stay alert".
