Ok we know that the shows should be in between episode 3 and 4.
We also know that most of the actors in the prequel would probably not reprise their roles due to acting commitments on major films.
that being said who would you like to see casted for the roles. Keep in mind that a lot of major characters form the original as well as the prequel trilogies could appear in various state of their life:
here are a few of my choices:
Grand Moff Tarkin:
Charles Dance for Tarkin. He looks the part and could play a slightly younger version of Tarkin. With good make up he would be spot on plus i believe he is british so that is a plus.
R2 D2 ( non CGI version )
the most obvious choice, nuff said about that one!
might be fun!