I believe it's currently impossible to be in 2 systems at once. Tell me if i'm wrong. I wanna be able to take down 2 planets at once for speed-running purposes.
Anyway, there could be achievement-like goals in bounty hunter, like "complete a veteran planet with a ship value of less than 100k" or "complete a vanguard planet in 2 minutes" or "have 10 million credits on hand" or "completely clear out 3 systems" (system being the groups of planets).
Completing these achievements could unlock ships for purchase in bounty and creative. (I find it slightly BS that people can just buy a Cerberus for 2 mill and beat the game). You could also have very easy achievements like "beat 3 planets" and have that unlock moving walkways or other parts. Partly because saying "hey look you have a new thing" makes people more likely to ACTUALLY use it. If you're going to do this unlockable parts thing, let people use everything in creative.
I know for me personally, if there are several unlockable rewards, i feel more eager to play the game. (not that I don't love the current game)