hey i dont know if it would be too late to implement this but this is just my thought
so far in the gal civ2 betas putting on an engine on any type of ship or hull will make that ship move forward a set number of spaces reguardless if it is a huge cargo hull or a tiny fighter
this dosnt make sense to me because since you can fit more engines on a huge cargo hull than on a fighter you will have your cargo hulls going faster than your small fighters which really dosnt make sense cause small ships are the ones that are supposed to go faster since the engines dont have to move as much
for balancing the small vrs large hulls i think that lets just say you put an engine on a fighter instead of it going only 1 extra space since it is smaller and thus lighter and easier to move you should have it go 3 or 4 extra spaces
now if you put the same engine on a cargo hull it would only go 1 extra space since it is bigger and would require more energy and engines to move
so for certain hull types engines should affect it in certain ways so that you can have nimble fighters with little firepower and great mobility and huge lumbering superships with massive firepower but little movement and of couse all the medium ships in between
plus this string had some good ideas on engine design as well
https://www.galciv2.com/Forums.aspx?ForumID=162&AID=85410#657391
any thoughts?