wabid said:

Cast Archetypes

The Robots

Jimmy Fallon - C3P0 Character

As much as I like Jimmy, can you imagine 3P0 biting his lip and cracking up with the giggles every five minutes?

James Spader - Tarkin Character

Not cold enough.

Billy Bob Thorton - Emperor Character

Whaaaat?

Alan Rickman - Dooku Character

Harvey Keitel - Gunray Character

Okay, Keitel in Star Wars? I'm in. But something big, like say Palpy Mk. II.
Imagine the throne room going a bit differently... "What, you just gonna stand there-that's it? Seriously? Make a move, do something! Nothing? Okay here's how it's gonna go..."

I don't know if these can be recast and maintain the same sense of character, but I do agree with above that the group of actors selected certainly have to be older.

But no one replaces The Dee Williams and his Colt 45. That's where we find Lando in VII-selling Colt 45 through the Outer Rim territories because some investments went very south. Think of it as the unreleased fourth Lando novel: Lando Calrissian and the rigors of selling terrible cheap malt liquor to aliens on sparsely populated backwater planets because you have a terrible business sense and were once the administrator of this facility.