One of the things I think would enhance the game would be to allow enemy ships to be captured during space fleet battles and planet fleet battles.
Also, all of that scrap metal from ships that are destroyed and no longer operable should be collectable and reusable (perhaps just reducing the time to complete ship building projects). Maybe some sort of a scrap metal collection ship type would be needed that can collect the scrap and then be sent to one of your planets to supply its ship building project.