I think the most interesting change for fighters & FAC/gunboats with a unified fuel consumption vs size formula is that engine size becomes a whole new and very important design consideration for small crafts.
A size 10 (500ton) FAC or small corvette engine will have close to identical fuel consumption to before but smaller engines will become much less efficient. Your still going to be able to have close to similar performance with the largest fighter engines, 6HS (300ton) will just have 29% higher consumption, but when going down towards 1HS (50ton) we are quickly losing out on alot of range or extra fuel needed.
This becomes an important trade off with fighter total size which you want to keep low to be able to get closer without getting detected, especially if more granularity to engine size is added such that fighters can be made extremely small using say a 0.5HS (25ton) or 1.2HS (60ton) engine.
Long range strike fighters could be going for pretty big engines for fuel efficiency similar to now, while shorter ranged Interceptors or Gauss PD fighters could opt for smaller engines to keep their size down and speed high, or get some redundancy when engaging enemy fighters thus sacrificing efficiency.
it creates a smooth transition for both engine types, which is more realistic and consistent, provides a bonus to larger ships, makes the fuel portion of missile design more interesting (as fuel is not a major concern at the moment) and allows larger engines to be designed beyond the current 50 HS limit. I could also add a tech line to allow the larger engines.
Thanks for considering my suggestion!
The formula ( SQRT(10/HS) ) is pretty flexible.
If you think that the fuel consumption difference between largest capital engine and smallest AMM becomes too extreme you can adjust the exponent (SQRT = ^0.5) to be something closer to 0 instead. With ^0.4 instead consumption for a 0.5 MSP AMM engines goes from 2000% -> 1098% and consumption for a 200 HS capital ship engines goes from 22% -> 30% thus narrowing the span a bit.
And if you want to shift the 100% efficiency "base" engines in either direction you just change the 10/HS to 5/HS or what size you feel should be the base.
I trust you will be able to find some formula that you feel work well here.