I have noticed that when you are sitting on the system screen you will occasionally have empty systems with no missions.
This is a perfect opportunity to do something unique to add flavor to the game play and mix things up.
I noticed the "Travel" button is greyed out.
A. Make the travel button "usable" irregardless of whether the system is void of missions or not. Why you ask ? Because players love to explore and even if there are corners that are dark and dusty someone (many someones) will go poke a light in that corner just to see what is there.
B. Allow a small chance for a "Unique" mission type - Special, Investigation, Priority etc and allow a bit larger chance for a regular type mission. Something like 1%/10% This way every now and then players can be surprised for their curiosity and exploration. With the chance being kept on the low end players will not hop in the system just expecting a special mission every time.
Summary- I truly believe that if you have real estate in a game you can have all of it serve a purpose instead of just looking pretty AND it should add to the gameplay diversity with surprise and more "Ah Ha!" moments since those are the ones we truly remember.
Again just my 2 cents =)
"Venerate the Immortal Emperor"