You could consider duplicating some of the equipment in your kit. Have your main kit in the front with you, have a secondary (partially duplicated) kit stored in the back of the vehicle, near the tail gate.

From what I’ve read, some fires start under the engine (or exhaust), even after the vehicle has stopped. Sometimes people have a few seconds to open the back of the vehicle and grab a few items before the vehicle is engulfed, so it may be worth having a small bag there too ? When we travel I have the SPOT in the front and the Sat Phone in the back, in the event of a collision or a theft, hopefully we would not lose both.