I vote Nexuiz GPM.
Slowing down the flag carrier was already voted 2/3 against it, was it not? Seriously, I love the system the way it is right now. With proper teamwork and communication Nexuiz GPM work well enough on the supposedly 'broken maps'. Once in a while in game, yes, you'll have someone score a flag with the laser in a few seconds but they have to plan that window!
I don't think you're giving enough credit to the minds who create such a situation that they can score that quickly in a well organized match. They'll be flying in open air anyway, you have 3 seconds to hit your target, I hope you fired a rocket at the landing point to bide you more time.
Punishing people that understand the game deeper than most will stunt creativity in movement. Don't put a governor on my Ferrari (reduce the carrier speed) because you're driving a Mercedes in a bad neighborhood (running around with your rocket launcher out near enemies camping snipers).
I agree with asserting a liability to the flag but I believe it should be done with points.