Indeed the drawback of not being able to capture spawnpoints while in a vehicle is a the risk of spawnkilling. I do however think it's a good feature, since ppl are actualy vulnerable when they want to capture a spawnpoint. This way you need to think twice before trying to capture a spawnpoint and often it's smarter to wait for backup; adds a bit of the need for tactics.
The new patch will make spawning players invincible for a couple of seconds. This is the countermeasure for spawnkilling. With that fix, I think spawnkilling is taken care of enough. Time to move on to other exploits and bugs.
Belly-button lasers! I've seen them!