Abandoned, updated version here:
https://mods.factorio.com/mod/impactproof-cars_v2

This makes ALL vehicles immune to impact damage. ie, crashing into stuff doesn't hurt you. This applies to vehicles such as cars, tanks, and those from mods (I've tested it with AAI, but it should work with most mods as well). Trains are NOT affected by this mod. Simple as that.

Note: Vehicles still take all other sorts of damage that they'd normally take. They are NOT invincible. Ramming straight into a biter nest... well, the impact won't kill you, but the biters might.

This is my first mod. I made it in maybe 5 minutes, borrowing most of the code from a mod on fireproofing trains. https://mods.factorio.com/mod/fireproof-trains All the credit goes to "alnet." The code is simple, and looks pretty bullet proof.