The one alternative rumored casting that I kinda like is Toshiro Mifune in place of Alec Guiness - and I liked Guiness in the role. It may be heresy, but I'd think you could have found a better Luke than Mark Hamill. Dennis Christopher, Michael O'Keefe maybe? Remember, the original started filming in 1976. For example, Tom Hanks, would have been an unknown 21 year - he wasn't even a professional actor at that point.