I would like to see one (and only one) new ship in Sins.
This ship is : The destroyer !
The destroyer would be a bridge between capital ships and cruisers and allow for less of a dependancy on capital ships and kodiaks late-game.
Destroyers would be multifunctional vessels, they would have 2 main weapon systems, dual gauss cannons to take out medium to heavy targets and about 4 Point defence anti-fighter guns. These ships would be able to hold 1 squad of fighters and would be the fastest late game unit you would have (second only to the scout vessels.) The destroyer would have no clear counter, it would be generaly good vs anything but not specialize in any specific roles. It would thus be quite a numerous vessel in ones fleet. Its size would be about about a quarter to about a half of the Kol's size and it would have slightly more hitpoints than the Kodiak. To prevent spamming, destroyers would take a long time to build (longer than any cruiser or frigate, but not as long as a capital ship, somewhere in between) and would have something around the price of 150 Crystal 800 Gold and maybe 500 iron. That way Destroyer spamming is out of the question. Since destroyers dont really excell vs any kind of unit you would need to support them with frigates and fighters to make them effective, they should become the backbone of your navy later on. Destroyer scanners are extremely effective and can cover a large area to help support your units.
Finaly, I think Destroyers should be added simply to mix up the current bland clear counters we have now. It would certainly be interesting to see them in the game !