I know what I thought the prequels would have that never materialized. I wanted to see Vader, in the suit, hunting down Jedi. I also figured that the Grand Moff Tarkin would have some sort of role, and probably a pretty important one, basically to explain why Tarkin can tell Vader off and he doesn't just kill him like he would any other imperial officer. Another one is that I expected Jabba the Hutt to also play some sort of role, due to the fact that the force doesn't work on him, and I figured for some reason that the empire made some sort of deal with him, maybe getting his help in the Jedi purge, in exchange for them letting him operate unhindered. Alas, none of these happened.