I like the suggestions you've made David, however right now I'm just trying to get through the rules as written.
Maneuverability appears to have two ways to modify the mass, volume, and power. The first is by vehicle tons and then TL. Cost is modified by the number of units by vehicle tons after the base cost is factored in.
Unfortunately, the base cost is the problem and I rather use 10k than 20k. I'm kind of cheap.
Weapon systems are usually more costly than most of the equipment installed. After weapons the cost is a toss-up between power plant/transmission/propulsion and electronics. At least that is what I've seen both in the real world and most gaming universes.