The only other way to keep Mustafar is to have the Vader (Palpatine) communion scene and have it say something that implies going to the place of Vader’s power, which of course would be Mustafar. However, now we’ve came full circle back to the point that Kylo’s face reveal at Mustafar is incredibly powerful and having another scene with his face in it would be weird if placed before that… this is starting to make my head hurt
This is why my alternative solution is to show him traversing the nebula, making it clear he still needed to follow the Wayfinder to get there, he didn’t just know where it was the whole time.
^^^^^This, I don’t think anyone is really fighting too hard for Mustafar at this point, but what is the problem with having an extra minute of Kylo exploring the nebula?