I would like a few systems strung together with certain objectives, through in a minimal story to make you care why you are their doing the same thing over and over. Add in or remove some units/techs based on the stories background and you have a campaign. Give us a character we can care about. Lowly Lt. Commander in charge of a frigate squadron rises to take charge of the whole fleet strategy sort of thing. Throw in some of those awesome CG movies to help tell the story and you have AAA game.
Hell the first THQ Warhammer 40K game had a lot less and still managed to convey a story of sorts across 6 factions. You also felt like you accomplished something when you beat all the maps. Here you feel like you continually skirmish without making any sort of impact.
I doubt they could do it now, but Sins 2 could expand the RPG element by giving loot. Equip your ships with parts dropped by other races or found in systems to change the beam color and stats of the ship. Give more fighters to a ship. Change its shields/armor/HP. Add special abilities, etc... The tech tree touches on this lightly showing that the current engine could handle it.