The idea of the Duel taking place on Vaders Castle and using Rogue One as a source for scenarios is one that I like a lot, but I would rather preffer a place more in the outside of the world than the castle, for example, some shots around 0:50 on the next video
https://www.youtube.com/watch?v=O84zsjLvOfk
More like mountains, rocks and that stuff, less of a big show for VFX and the Mustafar facility, Vaders Castle would be awesome tho, we could go even further and make it like an Anakin base where he is and stuff, but for the Duel, I would preffer the land rather than a building