I am currently playing Supernova 1.51.375185.1 under Epic Games.
Above is my impotent starbase. I should be able to attack the Mimot spaceship to the left as well as a lot of other targets. Alas, I am not given the option like I would if it was one of my ships. I know this was a problem in GalCiv4 but I thought you fixed it in Supernova. Below is what Starbase's capabilities are.
here is the save file. The starbase is "Deep Space Starbase 14" soon to be renamed "Cant get it up"