Maybe a way it could work is make the "laugh" something anguished, or a mix between laughter and screaming (as in: he is shocked when Vader picks him up, but he has the same attitude as Obi-Wan did at the end of his duel with Vader: "If you strike me down, I will only become more powerful...") thus, he screams out of fear of death, but revels in the possibility of becoming an energy being ala Obi-Wan.

Of course, his influence would be more like Sauron in the sense that he could only tempt and try to corrupt ala a haunting of a sorts.. or more to the point, like Nicol Williamson's Merlin in the movie EXCALIBUR ("A dream to some... a NIGHTMARE TO OTHERS!") after Morgana traps him in the cave.

BTW, here is a possible "Emperor's Crib" idea:

a posssible idea to kind of differentiate the 2 Death Stars is maybe make the second DS a little more angular and not perfectly spherical - to incorporate a more "temple-ish" or ancient world look. I would place the Emperor's "palace" on the artic (and to balance the DS, one on the antartic) pole of the DS, as a place to overlook "all of creation" so to speak.

Again, keep it subtle; the DS would still be "spherical" more or less, just not "perfectly" round (but nowhere near to the extent of say a "Devo hat")

This may be a good alternative to the BLACK HOLE overhead window in large room idea Bingo Wings had. You wouldn't have to show it in all shots; in fact, you could do a "pan down" from the large overhead window to the rest of the scene (say in one of the first Throne Room scenes) and play everything "as-is". Once established, the thought of it would be enough to help "expand" the scope of the Throne Room.