Cutting any of the emperor’s early scenes would be a mistake as he is the primary villain of the film (Vader is a protagonist in ROTJ, not an antagonist. I actually wrote an essay on this in college for a story development course). We need to see the villain being villainous BEFORE the climax of the film so we know him well enough and so we see how he actively is a force against our hero’s mission so we root against him. It’s not enough to have him randomly pop up at the end and act all menacing. As great as the throne room climactic scenes are, they can’t stand on their own from a story perspective.