The Leopard and Abrams have 120mm smoothbore guns. The Panther has 130mm. If we get past the "more is better" (which doesn't seem to be an issue as 120s can penetrate T72 armor), doesn't this seem to present a logistics issue?

That said, I see the motion towards a factory in Ukraine as more a desire by Rheinmetall to get out from under the control of German pacifists - plus a desire to have a battle-proven platform. Also, Germany's recent decision to buy F35s in place of the delayed Dassault fighter might have a bearing.

Good description of the KF51 'Panther' here.