Nice! Let me know how your setup goes. I've been looking at this system as well from Aliengear
ShapeShift Modular Holster System by Alien Gear Holsters
It looks to be easy to dismount then transfer to another mount that's in the car. That way your primary is just going back and forth. However I prefer to carry iwb, and want to have a dedicated rig that's always in the car.
Maybe something in the armrest box? That should be deep enough for even a full size pistol. Maybe find a way to lock that.