Alternatively, we could have Palpatine’s first line be “Empress Palpatine”, Rey turns around, and then he could go on by saying “long have I waited… you will take the throne.”
Still like your idea the most, though. Mostly because the above ordering still insinuates he has been waiting a long time specifically for her, while yours doesn’t as much.
Yours is: "Long have I waited… you will take the throne, Empress Palpatine.” Much more natural and fits the narrative better.