The one issue I can think of with the Naut being pre-war is that it means the tech was just sitting there out in the open, much easier to find than Gabe's designs in Paritus. If it was prewar, all someone would have to do is look at the wreak and then build from that. Also judging the time frame since the old world, the sands should have covered more of it.
However, lets assume it is old world. Where is the rest of it? We're only seeing a small segment of the larger vessel. With the amount of metal it has, it couldn't have all burned up.
So we've got possibilities for scavengers, say Nalm and Sylka have been pillaging it for their cities. That is one idea as to why we don't have more of it left.
Another is, perhaps not all of it broke off over the dunes. If we consider Dunes and Duel at Dawn two different areas then what we have is part of it breaking off over the dunes and the other part at where Duel at Dawn is. This means that perhaps the ship was more segmented in design, not one complete superstructure. It would have had multiple ballast systems for each segment. So it could lose one part of the ship and still stay in the air.
Given the level of tech for it and the geographic location, if it was a multi segmented ship, perhaps it's origin is Anglea. They have a lot of advanced tech there that is buried. Perhaps the naut was an early find that kickstarted their nation. Who would want to move to Anglea unless there was good reason? Finding something like the naut, would be good reason. Maybe Angleans used it as an early raiding platform until it was taken out? Like their own helicarrier in the sky. Hard to say.
