Here's some thought. OT has few sets. ROTS has a lot, some of which are barely star-warsy. So... wouldn't it be more suggestive if the "opera scene" took place in somewhere more familiar to us, a place where the Emperor could fool around and toy with his "new" property? (the same way some villains like to play with a small ball pretending it's the world). The scene would be a lot of less fancy this way, and it'd even be a nice shadow of the things to come (the building'd be empty, just couldn't find a picture of the empty building tho, so the viewer would start to think: wait, what the fuck's he doing there alone):

And this one; I made it for fun. Who's with me when saying that the senate cannot be purplish? Added a nice blink to the OT too, that's the place where he shoulda been. Just put him there and you won't have to explain why Vader's such a pussy with him; if it was doable...