I think, people should create their own team and try to mod that "realism" out of FH2. I would like to try that as well.
But to be honest, if I want more realism, I'd go re-enacting or heck, join the military.
Regarding separated driver-gunner position on tanks:
Pros:
Tanks will have more value, since it normally carries more player (more ticket loss per kill), and people won't go wasting the asset like taking risk on ditches, fording, etc. They will use it carefully.
Improve immersion, as it adds more role into tanking. Players need to communicate more and teamwork become necessary.
Gunner can't shoot as accurate when moving - that's realistic? But the tank will be more mechanical and fuzzy sometimes, the crew are more likely to be confused. Only l33t players would play tanks better then.
Cons:
My speculation says, we would see more tanks being used as transportation means. The player would just drive the tank, knowing that he couldn't shoot the main gun, he'll just drive away from the firefight and straight to wherever place he wanted to be. -well talking about some pubbies' attitude.
Gunner can't shoot accurately, driver don't react properly, because there is no commander. Commanders here won't have much effect since players can't be court martial-ed.
In desperate situation, gunner will bail tanks often (e.g. entering and exiting tank in quick succession), they will only use the gunner position when they want, and bail to avoid being sighted, making tanks another static guns (without driver). Therefore, less value for tanks.
IIRC, the first game that introduce tanking with its full crews is Op: Flashpoint (the grandfather of today's ARMA). We have to man 3 positions (commander, driver, and gunner) to fully operate an Abrams tank. But you don't always need commander to make the thing works. That game only have limited number of tanks, since it is more focused on the combat. It also requires 2 helicopter crew to man a Cobra, the other is completely a pilot and can't shoot rockets as in PR, the other one is a gunner, which has every weapon it carries on his dispatch. It used to be played by serious guys, they re-enact the game like true geeks. I believe general BF2 players are of lower qualities in this aspect, they are more of fun-lovers.