I find a major problem with BF2 is that most of the good vehicles work well by yourself. For example, tanks and APCs are driven and gunned by the driver, and don't need anyone else in them. This leads to people driving vehicles solo instead of teaming up. Having vehicles like the attack chopper and jeeps, in which the driver has limited or no weapons, encourages people to team up much more. Before it got nerfed, this used to happen with the Black Hawk helicopter.

Under this system, every vehicle with 2 or more seats would have significant benefits to having a copilot/gunner. For example, without gunners in the turrets, the Falcon  would only control the laser and/or missiles on the front, not much use. By waiting for those gunners, it becomes a powerful ship (unlike the BF2 bombers, in which the copilot has rubbish missiles).

Tanks shouldbe limited to anti-infantry weapons, and the gunner would control the anti-armor weapons, similar to Battlefront 2.

On minor capships like the vette and neb, you could have a pilot and up to 6 gunners, each of which would control a group of turrets. Even on things like the speeder bike, the passenger could fire his handheld weapon.

Also, most vehicles should have plenty of passenger spots, even if they cant do anything. The vodnik on BF2, for example, clearly holds space for around 8 people, but only holds 4. Pointless.