Assuming that Badspot fixes vehicles, which is actually one of the most important updates from my point of view, this could be somewhat possible.
The best idea would be to have like 4-5 "crash shapes" in a vehicle. Because blockland isn't super realistic, there would just be a crash for:
Top crushed
Entire thing destroyed (current deadjeep)
front crushed
back crushed
and that would work fine. The car would have 3-4 nodes, and assuming that vehicle --> brick collision is fixed, then which ever node was "activated" (By a crash at a certain speed, in the same way that bouncing is currently calculated), the corresponding "crash shape" would be taken on.
Sadly, this all hinges on vehicle --> brick collision not sucking.
Go Baddy, go...!
Edit: Obviously, this is a work around. However, it is a low(er) data solution that would work without drastically changing the way that vehicles are modeled.