Issue: An small enemy fleet is heading towards one of my unprotected planets. I have numerous destroyers and lighter cruisers in the area. I move some ships in to protect the target system. The next turn the enemy targets a different system, one that I just vacated to protect the first system, and is now 1 turn closer. I move my ships again, and the dance continues until they arrive at an unprotected system and quickly capture it (no planetary defenses there yet). I move my fleet to recapture and they just hop their cruiser one step ahead of me and keep taking my younger systems. If I spread out my ships to protect everything at once, then they get destroyed turn by turn in uneven battles. I have a superior fleet, but the way the game works I need to have a superior fleet at every single one of my systems that are in close proximity in order to fully protect them.
I haven't thought this through, but here are some ideas to ponder:
Suggestion One: Once a fleet is over 1/2 way on its journey to a destination it cannot divert. Alternately, once a fleet is within X (2?) turns of a system it cannot divert. This would allow me to set up an adequate defense without worrying about nearby systems.
Suggestion Two: Once a fleet arrives at a system, it has to "rest" for a turn before it can leave or attack. Alternately, once a fleet has attacked it has to "rest" for a turn before it can leave. This would give me a chance to pin down the enemy fleet and use my numerical advantage.