This is a world where military vehicles having souls is a thing that happens somewhere between "often" and "always". This tends to resolve the Ship of Theseus problem rather conclusively.

It's definitely not fair to force people to use tanks which saw actual combat before 1946, but there could be an advantage to a team who coaxes an ancient tank to life and treats him the same as any of the flesh-and-blood members.

Then again, a team who has built their own tank from the ground up and shows just as much care to him would probably do just as well. It's the caring that matters; the age just manifests itself in different personalities.