-Have the opening adventure not be tied to the main plot. KOTCS broke away from this cornerstone of the films, but it's a cool device that goes back to James Bond. Let's start off the film at the end of another of Indy's adventures
-Don't go out of the way to bash KOTCS.
-Have gunplay, have whip play. We haven't had a good shootout since TOD. Since Harrison/Indy is older, he can use his gun and whip more than his fists
-Make Indy an even dirtier fighter than in his youth. He's more clever as an older man. He can use things to his advantage younger stronger fighters might not.
-Give Indy a younger assistant, preferably female. Indy is best when paired with a woman.
-Have at best three scenes set in the US. Have the rest of the film take place someplace Indy hasn't gone yet. Africa? Vietnam? Ireland? Scotland (after all his dad was a Scot)
-Let Harrison have at least 50%-60% of the screentime
-Let Harrison be an active adventurer in this film. Don't make it where he is retired and reluctant to go out into the field.
-Use practical effects as much as possible
-Try to emulate the look of the first three films as much as possible.
-Mention the 1960s too much
-Don't make the film political. Given we'll be in the late 60s, this might be hard to resist.
-Don't make the female assistant outdo Indy or know more than him or take the spotlight away from him in the action department. Show her as intelligent and like Indy, but at the same time, not outshining him. Don't put feminism in an Indy film
-Use any sci-fi elements
-Don't use Russians again
-Don't make jokes about Indy's age. Preferably don't mention it, but if the film does, do it in a mature way, don't make him look like a doddering old fool.
-Keep mention of Hippies and/or 60s counterculture to a VERY bare minimum
-DO NOT refer to Indy as "Henry Jones, Jr." Ever. At all.