Eh, somehow I don't see Shivans as needing stationary outposts. They just aren't a 'defense' kind of species. In fact, the only Shivan object that can't be redeployed elsewhere is the Shivan comm node, since sentry guns are small enough to repack in cargo containers.
From what I can tell, they prefer to stay on the move, so their weaknesses aren't exploitable by enemies. They can carry plenty of fighters and bombers in their warships, bring along lots of gas miners and freighters/transports to cover logistics, and with their advanced subspace abilities they crush a species with frightening efficiency.
If they built an outpost, that would just be wasted time and resources since the Shivans wouldn't be able to take it with them when all enemies in the system are dead.