What if the Sathanases were not warships, but merely some kind of armed transport? They could be designed to do three things:
1. Gather lots of Shivans ('civilian' Shivans?) inside their massive hulls.
2. Build a supernode and go through it (probably 'home', as Petrarch speculates).
3. Mow through any node blockades on the way.
I don't like the supernode theory, but I must admit that it's the most probable one. Petrarch speculates about it, and if I were

, I would love it to put some hints to the solution of the mystery into the games (after all, the Shivans still are a mystery to us) . After playing the whole -intended- trilogy, the player would get the feeling of 'Hell, why didn't I see this before?'
But wherever the Saths were going, I don't think they would be going there to wage a war. Even a Sath can't operate without support for too long. So what were they going to do? The Terrans and the Vasudans - even before they met each other - have two kinds of ships: warships and transport ships. Therefore, this is probably the same for all species in FreeSpace. Now if the Sathanases weren't going to wage a war there (= wherever they were going), they're probably not warships. What's left? Transport vessels. The Saths would be the Shivan equivalent of our GTM Hippocrates.