We already know Volition were talking about planet-sized vessels, I'm assuming Shivan unless the '3rd' was to be set several thousand years in the future, so it's already certain that there is more than is in ships.tbl, I don't see even the Shivans being able to construct a ship that big outside of a considerable amount of time. Since we are talking hypothetical here, what if that was what they had in mind for Shivan 'worlds'?
Personally, I don't see the Moloch or Sathanas (particuarly the Moloch) being 'new' designs, the Mara and the Ravanna, however, I could almost accept it, they are almost a direct reply to the Terran vessels of FS1, the Orion and the Apollo/Ulysses etc, but built to Shivan standards. The sheer quantity of the Sathanas suggests to me that it is a workhorse of the Shivan fleet, which is a scary thought.
But then then it does not explain why a ship nearly 8000 years older has shields.It also means that the Demon Class vessel must also be extremely old.