Ugh - I LOVE Indiana Jones, but can't they just accept Harrison is too old for the role and recast it. There are some really good Indiana Jones stories out there in comics form that could be translated into great movies.
Although - set the movie in 1980 with a 75-year old Indiana Jones hired as a consultant on a movie based on his real-life adventurers during WWII called "Raiders of the Lost Ark" in which they stumble across a real-life cursed artifact that starts picking off the players one-by-one....