So.... anyway. As Matt said, an updated Vehicle Handbook is a year or more out. In the mean time, let me float this idea about adding back Fusion Plus as an option (which I 'believe' in as much as M-Drive, but hey, it's a 3I thing for sure):
This is just a preliminary thought, but I wonder if it would work:
TL10: Cost per space (of vehicle) Cr50000, Endurance = 30 days at cruise speed, 20 days at max speed, 360 days at minimal power (stationary with the engine running for life support, etc.)
TL13: Cost per space (of vehicle) Cr100000, Endurance = 60 days at cruise speed, 40 days at max speed, 720 days at minimal power.
Refueled with water, or at Cr500 per space with deuterium given 10x duration. Does not require more spaces, just replaces the 'normal' engine and fuel tanks with Fusion Plus units.
This is pretty much taken straight out of the updated CSC (p.117) and a medium-sized generator, which is really just ~2-3 kW or 3-4ish hp, so it might be weak if taken literally. It may instead make sense to make it a 'faster burning' reactor and cut the duration by 5 or 10 to up the horse (or poni) power to enough to give decent power to a vehicle.
Just thoughts at the moment, but it might make vehicles work more like they 'should' or did in the Classic adventures.
And if we cut the duration by 10 and then use heavy water, then we get back to the duration above, net ~25kW per space output, which given an 8-space ground car is about 150 267 horsepower. Close enough. You can still play with the VHB performance knobs for variance.
(edited for bad math)