[Baron Munchausen]

Yes, increasing hull costs for larger ships is a good way to help balance the game. Also giving smaller ships a movement bonus and defensive bonuses in combat. Or even giving larger ships defensive penalties.

I think 'QNP' (Quasi-Newtonian Propulsion) is a good way to help make ship size classes reflect real-world limitations. The other obvious way, with turn rates and weapon arcs, is not available in SE IV. Hopefully this will be available in SE V.