In principal you can do full physics track as a chain of treads with collision mesh, connected to each other using physics constraint. There is a working example of this in Tracked Vehicles thread. Main problem with such approach is performance and stability of joints. Stability can be fine for low velocity but at something over 20km/h things will go ugly.
I have some ideas based on modifying shape of the track spline by raytracing multiple points against the ground, but nothing concrete yet.
With current implementation you can always add some small invisible spheres with collision and drag track by them. I could actually try this.