Vehicle limits are in place because of technical limitations. There is a certain asset/memory budget CCP has to work with in order to not decimate the performance of the game. It's one of the main reasons they switched to the Unreal engine.

I agree, it kind of sucks for vehicle pilots but it's in place to prevent us all suffering from lag if the enemy DID decide to bring 16 HAVs into the match.

While I understand your point, I wonder if it's really the case. I would think vehicles would probably have a smaller, or at least roughly equivalent, computational budget when compared to dropsuits. It's not like vehicles are more complex than the dropsuits.

To include dropsuit weapon types.
As I understand it, the vehicle limits are there to prevent vehicle spam. In other words, the limit is there to prevent a team from facing a team of 16 HAVs say.

Please do the same thing to prevent weapon spam. Limit each side to say 8 of each type of light weapon, sidearm, heavy weapon to prevent a team from facing another team which is comprised of all one weapon type.