I don't want to see anyone particularly well-known in Indy4. Anthony Hopkins is a good actor, as someone said, but to me he's always "Anthony Hopkins" because he's entirely too well known, and his face is all over the place in magazines and such. Same problem with Harrison Ford, lately, but fortunately, I can still see him as Indy.
I liked the leading ladies in the previous Indy movies because I only knew them as their characters. Karen Allen was Marion. Nobody else. I'd never seen her anywhere before Raiders, so I didn't associate her with any other character. Same with Kate Capshaw and Alison Doody. And of course I can also say the same about other characters like Mola Ram and Belloq and Short Round. I didn't know these people from other roles (yes, I know now that Paul Freeman and Amish-what's-his-face-Mola were in a ton of other movies, but I hadn't seen them before Raiders.) While I loved Henry Jones, Sr., I couldn't help but look at him and think, "Wow, what a weird role for Sean Connery." Rather than him just being the character, he was the actor too, and that takes a little something away from the experience for me.