Short term:
Fluctuate your timing of maintenance.
Having it at roughly the same time every time penalizes people with limited schedules. I see the notice of scheduled maintenance and know that it's another day I won't be able to play at all due to the schedule falling right into my limited time.

Medium term:
Housing, or a better way to group community built missions. Although last time i played I discoverd visiting other parts of my ship, so we'll see.

Long Term:
Play Romulans.
Play older eras of Star Trek with period version ships.