Community manager Eric Musco explains that the developers have been going back and forth on the best ways to reward players for their subscription time, but the best way to find out what players want is, well, to ask players what they want. A short survey is linked on the forum post with a variety of options for what players would like to receive for added subscription value. It seems like a straightforward way to figure out what players want as a whole, although “personal Death Star” as a reward might have some balance issues.
Source: Official Forums via Dulfy