Then there was the real secret ComGuards army which had SL-era tech (but certainly not exclusively!). They were only rarely deployed. One cool campaign would be the termination of the Jolly Roger pirates in the periphery in 3004: Jolly Roger Affair. This was top-secret and completely covered up. (Probably because most of the inexperienced ComGuards died at the hands of the pirates, suffering a 2.3 : 1 kill ratio.)
This.
Also, they could be placed on extended training maneuvers in the Periphery hunting pirates and/or hunting out additional Star League caches or equipment primarily to keep them out of the hands of the Successor States and Periphery powers. Or, they could be attached to the Explorer Corps mission.
For a non-combat heavy game, the Explore Corps idea makes the most sense. The Corps would need experienced Drop/JumpShip pilots & crew, diplomats, security personnel/infantry, technicians and scientists, etc. Also, the Corps was used by ComStar as a dumping ground for malcontents and troublemakers, so it is just the sort of unit that PCs thrive in in my experience.
"Space: The Final Frontier. These are the voyages of the JumpShip
Jerome Blake. Its five-year mission: to explore strange new worlds, to seek out new life and new civilizations, to boldly go where no man has gone before...and bring the heathens and heretics into the fold of humanity under the diving light of Blake's teachings."