The issue I have with the bridge shot and moving the Vader (other than kylo losing his motivation to build a new helmet) is that the the first shot of Kylo on Mustafar is a very “establishing” shot, like it feels like a reveal. A “here’s Kylo!” moment. If you place the bridge or helmet moment first, then the first shots of Kylo are kind of underwhelming. But then they’re immediately followed up by a dramatic reveal of his face fighting. In all the mockups people have done it just feels disjointed.
Just my two cents