An interesting idea. In the original Tradewars you could move your planet to a different sector. If we were to do something like that you could only move your planet into sectors that had an open slot for a planet. If it is a 0 planet sector you can't go through the sector and have to go around it. If it is a 3 planet sector and there are three planets in there you can't go through it. You would have to capture and blow up one of the planets or go around the sector.
I would probably tie it into the Autoroutes created by the Navcomp. You would create an autoroute in the navcomp and then tell the planet mover to use that route to move the planet.
I would also make it take a lot longer to move the planet than every 5 minutes. It should take 12 hours to move the planet from one sector to another. So if you want to move through 5 sectors it's going to take 2.5 days to do it. I like the idea that it is vulnerable to attack because while moving you can't place sector defenses.
I would also put a restriction on moving planets into SG sectors. Otherwise people will end up moving everything out of realspace into SG's. I know people end up building like that after a while but there probably needs to be some restriction of some sort.
I like the idea.