Here’s my shitty proof of concept for extending Mustafar:
Clearly you can see here that nothing really works with this clip as the video quality of the added shots is very poor as well as the added music.
I think you are on to something. Perhaps when Kylo uncovers the stone chest and grabs the wayfinder, instead of panning back to him holding it against the backdrop of the forest you can show an establishing shot of Vader’s castle from Rogue One instead. Just another link to him and his grandfather and shows the audience it is indeed Mustafar. You can make it look like he is in the interior of the castle retrieving the wayfinder instead of outside. Just an idea. Keep up the good work!