The noquit flag, or a timer would probably work the best. If a simple 30s - 2 min timer was activated when you wanted to quit, you would just have to watch and wait. But it would also have to have a quick exit dialog, so in the case your position becomes unsafe within the time frame you can defend yourself. 5-10 seconds would not always be enough time to kill another player before exit, just going prone they could possibly last that long, not to mention if they took cover behind anything. During long engagements someone could potentially wait a minute or more behind cover for a logout timer, before the enemy even got to their position.
