I think you are really onto something here but I don't think Palps needs to turn the lights down.

Just by using the force he could screw up the electronics in the room (you could add the Darkside hum from ANH in there, like when Vader does the choke thing).

I'd go for the same sort of periods of darkness you already have in the anti-chamber (but start with the lights stuttering off) in the chamber beyond however I'd have them strobe like crazy (baring in mind that the city lights through the window would stay the same).

You could even sneak a few shots of prune-faced Palp in there mid strobe like he's already losing his grip on his nice guy mask (think Captain Howdy in The Exorcist).

This would be a great way of hiding the awful transition from Chancellor Palpatine to Emperor Sidious.