[Christ]

Build a trailer that will drive with EV power, put a small hitch on your car, then when you're going to be on the highway for a long time, use the trailer to push you along (at least partially) so that you're using less fuel for the same speed. It's simpler than trying to dig into your (still under warranty) car and modify things that aren't easily reversed.

An EV pusher trailer also means that you don't have to keep pulling the extra weight around when you don't need it, and can be shaped to give you some aerodynamic advantages as well.