The problem is that models are just visual details.AFAIK, it isn't possible. If more people show such an interest, I can ask the team about it. TBH, though I would prefer only the advanced model. Jmo, ymmv
You do know that ships obsolete by 1 generation can still be produced, right?
New techs will allow stats development and there is no gameplay reason to keep the "old stats" when the new unit is just better.
I cant see any need in such a feature.
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