The problem with leaving in “I am all the Sith!” is that Rey’s new “I’m a Jedi!” response has to specifically be to Sheevie’s “a SCAVENGER GIRL is no match for the power in me!” statement, right? (edit: just as the poster above said!) Perhaps swapping Palpatine’s lines would work. Here’s a crude mockup of that idea (forgive the unpolished audio and lack of ghosts).
Edit: Does Rey ever refer to herself as a Jedi before this? I know Luke does, but I think that’s alright. It’s just that for this to land well, I think it has to be a ‘breakthrough’ in her confidence in herself, overcoming that self-doubt (which would be undermined if she’d previously considered herself a Jedi).
This is one of those special edits. Such a simple change, but brought a smile to my face each time I watched it. I wholeheartedly think this is the solution. It keeps “I am all the Sith”, which allows Sheevykins to boast a bit longer before Rey slays him, which I think is better for the pacing of the scene than outright removing it. (Also, “You are nothing, I am all the Sith!” flows perfectly as a single sentence) But it still maintains the change everyone is loving here, where Rey retorts to being called a scavenger, not to the Sith comment. Well done!