The only idea I can think of to help support the ‘mask’ approach would be to change his appearance anytime Palpatine is disguised as Darth Sidious before the transformation. So when we see him with Maul on Coruscant in TPM, or with Dooku in AOTC, you could either desaturate his skin to be similar to his deformed look, or use deepfake technology to replace his regular face with the deformed face. It would be harder to implement this with hologram appearance (like his conversation with Grievous in ROTS or with Nute Gunray in TPM. Maybe you could obscure his entire face in darkness, or do something similar to what Ady did for ESB:R), but this idea could help make it clearer that Palpatine has always looked like that, but has just hid his true form with his ‘unlimited power’. But for LOE, I think it works fine and is still better than the theatrical, like Dom said. Might be something to consider in future edits though.
Yeah that would be a good solution, if feasible (unlikely, unfortunately).