I'm not too sure how to describe this.
I would like to see a camera mode that combines normal and freelook for vehicles that when you're controlling the vehicle, it acts as per normal camera mode, but using the mouse causes you to move the camera as per free look, but after a small delay, snaps back into camera mode. A system (if I remember) that was in GTA4, allows for partially passive camera control and full control without a toggle.
This would be in addition to the two modes that exist now, for clarification.