Unfortunately, it seems that none of the big three feel that way. Their comments about "learning something new about the character" with every film have less to do with Indy as a person, and more to do with the people in his life from ROTLA on, if you go chronologically through the films. I think the "stand alone" quality of the films is a GREAT concept, but one that is getting increasingly difficult to pull off with all the tie-ins. How can a film stand on it's own if it's expected to carry all the personal baggage from one film to the next? Plus add more with each consecutive film? It's a daunting, cumbersome, and unnecessary task in this fan's opinion.
I think there is plenty to be learned about Indy that could be conveyed with a simple facial expression or Indy's decisions/actions, without having to drag a fleet of recurring characters along. Heck, I think that we'd learn MORE about his character by being introduced to other people from his past that actually have something relevant to add to the plot. Read: more screen time for a character like Mac, less screen time for a character like Oxley. After all, Indy is a world traveler who has globe-trotted for his whole life, and had "many adventures". Surely it's not necessary to stick so close to home with plot devices like Marion being kidnapped twice, and his father once. Sure, let him save someone, but how about someone new for Indy 5? We never new Marion before ROTLA, and we were able to care about her character right off the bat, after all. Heck, try a different twist. Have him fail to save someone, but succeed in saving "the world" or whatever. It's in keeping with his origin story: He left Marion tied up to get the ark. He didn't blow up the ark, either.
So again I say, Indy as the only recurring character, unless it's absolutely necessary to show some exposition scene stateside. My opinion on the matter of course is worth about half a bucket of warm **** (give or take a drop), since George has said recently that
he already has the plot worked out, anyway.