How about a compromise; being in a vehicle that has potential to drive away/absorb bullets shouldn't make you an easy target for fearrp, but also being shot at once shouldn't make you fearless to anythign else. Thus, what if nobody can be fear-rp'd out of cars, however if your car begins to start smoking its durability is compromised and you're more willing to cooperate than to risk further desctruction to the car or the occupants. You could even extend this to LAVs and insurgents, because AFAIK the smoking effect results after achieving a certain percentage of total health, so their naturally higher HP would mean a lot more work to get it to a state of disrepair, keeping their high endurance. Just an idea.
To be honest, yeah, I see both sides of this argument here. Many factions group up near the checkpoint just because it's fairly accessible for everyone and allows for RP. This means that for anyone wanting to take the logical exit becomes a natural target for any trouble-makers. Furthermore, many new people can become discouraged from what appears to be being spawncamped from outside their base. Unfortunately, the Registan base's second gate is sort of hidden, and I rarely see people leave from there. For the officers, well, it's a lot easier; you can just spawn a car over the wall — the USMC bunks are quite far from the auxiliary gate. However, it should be accommodated such that non-officers have ease of access to leave base, as they make up the vast majority. For Registan particularly, we have two vehicle dealers near the main gate, and none near the side. Why not move one of the vehicle dealers to the side area so that there is reduced clutter on the main road and less tediousness navigating the sharp turns to the second gate?
In summary, I see where you're coming from Ben and I agree that it is an issue, but it's just how it's come to be. Taliban want to kill US, it's their purpose, so you have to find grounds where you're at an advantage, not them. I find that leaving base with a rough idea of where I'm going makes it easier to determine where to leave from, how to leave and to avoid certain areas. When there's an AH-6, it's like playing cat and mouse, you can't really fight it unless you're at base or on an objective with multiple people, but you can try and avoid it best you can. For some reason, the gate-camping ordeal only became an actual thing during ww3, that or I can't remember it before then. If there is a troublesome person/group hanging near the US base with murderous tendencies, I'd try to gather up some people or go myself to flank them and take them out. It leaves the majority of the people in checkpoint wanting to RP unaffected, but keeps the US safe.
On a side note, the people that like to stay in towers to avoid having to continually dying and going to capture objectives have a fair way to play the game, I always see Taliban and US interacting in the checkpoint and I think that a few people defending in the towers and conversing with civilians is healthy for RP as well as balances the others who like going out for PVP and objectives. During raids/random events/vault, most will be told to come assist anyway.