They should keep it how it is. If they make it so you need a second person for gunner then it is going to be a lot harder for new players, casuals and loners who hate aircraft and don't feel like sitting in a bus and will make them not like the game at all. Or even worse dozens of tanks with no gunners ramming each other.
Then new players would need to buy mics, so they can communicate with their gunner or driver. Some of you hardcore guys may never have experienced this, but trust me I have witnessed this before and something like this is a deal breaker. Unless of course if you don't care that your gunner is looking at a soldier behind you when five tanks are in front and you are yelling in your head because you have no mic. Driving a warthog in Halo with no mic jeez...
Ever fill out a form or sign up thing online and then it says you have to fill out a survey to continue? You say to yourself "Well I'm done here, not wasting my time." Kind of the same thing with two people for a tank.
New player sees the tank and he can't shoot, "Well I'm done here!"