If this suggestion has already been posted, forgive the redundancy....
How about a research option that would allow one to create a Planetary Gateway that would provide instant fleet transportation between your Capitol planet and a second planet you own that is located anywhere on the map.?
(you would probably choose your 2nd most valuable planet, either a wealthy one or one that is a strategic/ tactical location.)
This should be invisible to an enemy (unless they research invisible gateway detection
, it should be expensive,
and you can only connect 2 ( or maybe 3?) planets. This would certainly be a great defensive help, and might be good to help launch a sneak attack.
Just thinking aloud. Anyone, feel free to chime in!
orion314159