There's no battle lines in space; ships can go anywhere, they only get in trouble once they get there. For example, the entire Kuvexian fleet could attack any single planet, but if they did, the planet would be able to warn every other world in the empire that the entire fleet was there, which would result in it getting outmaneuvered and obliterated. So, fleet commanders need to outwit their opponents, they can't just target a 'defenseless' system and claim victory.
When a scout ship shows up, they have to be careful, because to a certain extent their arrival and actions will tell the enemy what their commanders are thinking, and help them zero in on the location of the fleet that launched the scout mission. They only need to be able to outwit the system defense vessels in the short term, but their mission might have to be cut short in case reinforcements arrive to intercept them.
I think logistics ships will only get in trouble if they have to run a blockade, or if they stumble into a battle due to late warning and/or poor communication.