Well I can't help thinking that with all the rights to the franchise still in certain hands, any reboot would be tragic. So here is my list of "tragic" casting choices.
Luke Skywalker: Daniel Radcliffe
Princess Leia: Lindsay Lohan
Han Solo: Seth Rogen
Obi-Wan Kenobi: Ewan McGregor
Darth Vader: George Lucas (because the trilogy is all about him)
C-3PO, R2-D2, Yoda, and Jabba would be CGI, of course.