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).
I really like this version. I feel like removing the “all the sith” line makes palpatine’s “you cant beat me” speech a tad short. Also, it really helps soldifiy the “all the sith spirits live in me because of the essence transfer”