It's definitely not an ideal environment for a number of reasons, but my past experience with a Harman Kardon Logic7 system in a car makes me think it is still worth pursuing.
The center image will be to the right of the driver and to the left of the front-seat passenger (LHD car), which is actually the way many car audio enthusiasts prefer it, but I don't. I prefer it to sound like it's directly in front of each occupant. The Logic7 algorithm mixed some of the center into the left and right channels, so one could lower the level of the center speaker to shift the center image over to in front of the occupants. So I'm expecting to be able to do the same thing, experiment with routing the center channel into the front left and front right at reduced level to move the center image over. Not a perfect solution, but everything in a car is a compromise.
For the side surrounds, far forward on the rear doors, which will put them within 6 inches or so of being next to the front seat occupants.