Another one off of my head, though I'd be very surprised if it hasn't been suggested in some way before:
Changing the way power plants and thrusters both work.
Specifically, Power-Plants now require fuel to operate, demanding a given amount of fuel per power-hour they produce. Like with engines, if they are not using their full power, they do not use their full fuel consumption. Like with engines, their efficiency is closely related to both their size, and their 'boost' out put, with high efficiency 'commercial' engines having low total output and large size, and on the other end high boosted engines being much much less efficient, but much smaller and with better total power outputs. The explosion chance upon destruction would likely remain.
The big thing this would change, however would be that now,
everything requires some degree of power output.
- Active sensors require power based on their active element and their size. This means that there's good reason to make a low power-ed active element, but highly sensitive sensor.
- Passive sensors require power based on their size.
- Shields require power in a manner which would functionally mimic their fuel use previously.
- Missile Launchers require power to fire, based on size. This would be to imitate the loading mechanisms at work. Reduced Launcher Size reduces power need at the same rate it reduces reload time (with box launchers requiring no power)
- Jump Drives now Require power based on their total jump tonnage, but possibly with efficiency inversely proportional to their mass efficiency.
- Cloaking Tech requires Power, again, based on it's efficiency.
- All other 'non designed' technologies require power as well, with the exception of fuel tanks.
- last, but not least: Engines Require Power
Engines, in this case, would no longer require any fuel to operate. This is because, rather than being based on our modern understanding of Newtonian physics where fast thing goes out back, ship moves forward, they instead impel against the Aether/Sub-Space in some way. Making this single change alone, however, does certainly flatten the granularity of engine design, which is why I propose a pair of further additions, this time onto Engines: Top Speed/Cruising Speed and Acceleration. They might both be taken, or neither.
In the case of Top Speed/Cruising-Speed, the power necessary to operate an engine could be on a curve towards 100% at 100%, such that at 50% speed the engine is using less than 50% power, and thus, less than 50% fuel. Boosted engines would basically expand the curve, while more efficient engines would shrink it back. More powerful engines produce more engine power for a given amount of power input, thus producing a different function of efficiency to speed.
Alternately, one could include acceleration: Ships now do not automatically go 0 to x000km/s But require some time to accelerate towards their top speed. More efficient engines are slower to accelerate, while less efficient engines have much higher acceleration. This could be combined with the concept of Top/Cruising Speed by having engines use their full power requirement during acceleration, but require only HALF power when above or below a certain speed threshold. A 'Commercial Engine' in this case would have it's cruising speed BE it's top speed, but perhaps still being inefficient in size, while a fighter or missile engine wouldn't have any cruising speed at all, but be at reduced size.
In this case, 'Acceleration' also becomes the measure of maneuverability, rather than top speed. Determining how quickly a vessel can change course, how easily it can avoid enemy fire, etc. (In the case of the former, perhaps the percentage of acceleration compared to top-speed functionally determines how fast it can turn within a 5 second interval).
I dunno. A lot of this was written while forced awake by nasty gas pain.
