Maybe I'm missing something or maybe I'm on to something. But I feel like if you can create a trade orginization in a system you should be able to control the path in which the route moves. I have had in every play through a trade route that could easily be re-routed a planet over in order to prevent a blockade. My fix for this would be to allow for custom trade routes where you can only add one or two additional nodes to bypass a system. This may remove some strategy to the game but perhaps if an enemy wished to block the route maybe let them use a scout ship (which are fairly under used in the late game) to find where these routes are, or only probes can spot trade routes after a certain tech. Another option is allowing players to spot enemy trade routes in their influence zone aswell