Prepare for a huge wall of text.
I just realized something. The Vanduul Scythe is a medium fighter, right? Wouldn't that mean there are light and heavy fighters?
But the Scythe is already very fast and maneuverable. What, with two main engines and 16 maneuvering thrusters (according the the specs page, though I thought it was 12).
So, what would that mean for a light fighter from the Vanduul? And why have we not seen it? Perhaps the Scythe is already fast enough. But if that's the case, what are all the light fighters being used for? And for that matter, where are all the heavy fighters?
The Scythe already carries a nice payload, according to the specs page, so they wouldn't need heavy fighters. Would they? Well, we've only ever seen the Vanduul in dogfights with other one-man ships. Perhaps the heavy fighters would be used against a larger ship, like a Constellation.
Because of the Vanduul's warlike nature, we can assume these ships to have very high quality weapons systems. But that brings us to the question: Who's making them? (I got this from an SC video I watched at one point. I forget what is was, but it covered the various ship producers in the game.) Judging from the interior of the Scythe, we can tell it is of very high quality.
However, this goes against all we know about the Vanduul. They work in mobile warbands, claiming everything they find for themselves. And they're ruthless, killing off entire planets. But they only fly their own ships. And luxurious ones, at that! This would mean that, somewhere, Vanduul are making ships.
But why would they do this? Surely they can just use the ships they take (I can assure you, every single ship on the planet doesn't explode after the Vanduul raid it), instead of making new ones. They also make weapons, as shown by the aces in AC, who have personalized loadouts. This means that they're not just making ships out of scrap, so they can raid things. These ships are very well made, by some Vanduul organization(?) who takes pride in their ships.
However, the Vanduul travel in warbands. They don't have planets covered in cities where they live, as shown by the very structure of their bodies. So they couldn't have a dedicated ship factory. Could they?
Well, we already know the Starfarer has an addon to manufacture fuel in space. This, in theory, proves the manufacturing of stuff on mobile ships possible. Except, fuel is a far cry from dedicated fighter ships. To make whole ships, you'd need ships as big as the Idris dedicated to manufacturing.. Which is a completely legitimate idea, considering how the Vanduul work. Not to mention, we have no idea what goes in in deep Vanduul space. There could be whole "warbands" dedicated to manufacturing ships and luxuries.
Case and point, aliens ships are amazing.