Think about that a bit more.   

Limiting a pilot from taking off has at least 2 issues.  
First:  What if he or she is playing and paying by the hour. (long distance calls or our Euro friends)
Second:  There are only 2 fields left.  And you just got vulched at both.  3 Minutes is an eternity.   
   Defensive strategy cant be played in these kinds of arenas, unless you are doing a scenario-type of game play.  Right now, it is usually a few trying to save a field.  That is pretty close to real life.  Maybe NOT allowing them a transfer TO the base being mobbed, may be a solution.  Say fuel or ammo restricts their entry.  That is in place now.  Hope you can see it from the bigger picture, but keep the thought process going!   

KKEN