Or, if we go back in time and have a new face
play Indy in his 30s, he could just still be alive.
Yeah, doesn't sound too sensible, but with a bit of Hollywood magic, he could pull off a short mentor like role. Think Marcus in Raiders
And before people point out the (supposed) irony with thinking Sir Sean @ 85 is okay but Harry who is 12 years younger isn't - the distinction is that he is not supposed to be the centerpiece of the film in his advanced age.