You are right that there is a discrepancy between what we are trying to roleplay and what we can reasonably do ingame. If the old Marduk were still buyable, which is something I asked for in the past, we would have opted to use that to represent our elder Nomads. However, as it stands, the only battleships that are available are the Ishtar and the new Marduk. I can now chose between not allowing my members to use battleships at all (and they would still need to have earned it through our progression system to get to that point) or I can live with the fact that we currently cannot not to use the 'newer' Nomad ships with the upgraded models from a gameplay perspective. Yes, you are absolutely right that the justification we tried to come up with might be rather flimsy considering the Ishtar is the result of 20+ years of Nomad evolution in Sirius — although the Vagrants also weren't stagnant in their separation from Sirius — but it is the best inRP explanation we can give at the current time. I hope that a more satisfying solution can be found at some point, but for now, I hope this will at least answer your question.