I realize my idea was hokey, but I think a big problem is that KOTCS locked Indy in too much, that getting a satisfactory Indy V would be very difficult. He is married now, with a son. Henry, Sr. is dead. He is an Assistant Dean.
Going into an Indy V, you can't just forget the existence of Mutt and Marion, even though it would be ideal, that would never happen. You can't kill them off immediately or else that would be hamfisted and would come off badly. If Marion is in the picture, that means you won't have the old womanizing Indy. If Mutt is there, he'll take up some of the action (which is something we DON'T want) and a good chunk of screen time given Spielberg's mancrush on him. Which we don't want either.
So either you'd get a movie which basically ignored the events of KOTCS (which would never happen) or you get a Jones Family Adventure, starring Mutt Willians and co-starring Marion Ravenwood and Indiana Jones. Which no one wants.
It isn't like The Mummy franchise where the actor who plays the lead adventurer is still young. Brandon Fraiser is only 43 and thus despite his character being married and having children, he could still do pretty much any sort of action scene believably without it seeming hokey. Also that series isn't forever bound to the massive ego and stubbornness of George Lucas. Indy's fate is.
Indy V, even if they filmed it this year, would feature a 70 year old Harrison portraying a 50 or 60 something Indy...Not much room for believable stunts ala the original trilogy. Not jumping on to tanks. No going under trucks. His role as a man of action would either have to be utterly muted, which is something most Indy fans wouldn't go for, or have it mostly handled by Mutt, which again is something most Indy fans don't want. And they can't even do any outrageous stunts: How can you outdo the Nuked Fridge without being even more cartoonish? How can you put Indy up against something which surpasses that unless you have him face down a demon or Cthullu?
Really, KOTCS painted Indy into what I see as some rather inescapable corners. The only options I see are going for either a Hitchcockian or Twilight Zone-esque Indy V and somehow giving Mutt and Marion as little screentime as possible, which can be done. Or doing something truly radical and having Indy meet Cthullu or something.
The idea of Indy and the Bermuda Triangle and Indy actually facing a terrifying monster, something right out of Lovecraft's works, would be interesting....
But sadly the most likely scenario is that the last we'll ever see of Ford's Indy is him getting married in what was a mediocre film--That the series will have ended with a whimper rather than a bang...And that saddens me. Indy's final farewell deserves better than what KOTCS delivered, which is why I hope against hope that a good Indy V is made to finish up the series and give Indy a truly respectable ending, worthy of the character who went through the events of the original trilogy.