Random, admittedly half-baked idea: turn the TROS scene of Palpatine talking to Pryde into an ANH scene of Palpatine talking to Tarkin. Don’t know how feasible that would be, but it might be a good way of incorporating the Emperor into an alternate version of the only Lucas movie in which he doesn’t appear:
“The princess of Alderaan has disrupted my plan. But her foolish act will be in vain…send the Death Star to a world they know. Let it burn.”
That would be an awesome way of getting some Emperor in ANH!