5. The Story
Remember that at one point there was a treatment written by Shane Black for Lethal Weapon 5. Richard Donner revealed the story they were going to go ahead with (though it's unclear whether the story is Black's or Donner's own). "The two crazies decide to cool their lives, but it's impossible for them to stay out of situations. It starts with Riggs and Murtaugh out in the country in a motorhome. They're on a trip and they stop to get gas, but Roger forgets to put the brake on. So the motorhome rolls through a village, annihilating everything, and they get in serious trouble. It had a lot of heart, a lot of family. Rene (Russo, who played Lorna Cole), Darlene (Love, who played Trish Murtaugh), they would all have come back."
I'll be honest. That little tidbit gets me excited. How great would it be to see our two favorite bickering best friends back as they attempt to navigate retirement. Sure, a bad writer could turn it into the hokiest thing since Glover's own Gone Fishin'. However, a writer as strong as Black could find the real potential in a story like that. We could see a funny film about our two favorite detectives retired and still get a meaningful theme about men of action being set out to pasture. There's a lot of potential with that story or any other story involving Riggs and Murtaugh (they'd all have the same them of retirement I'm assuming).