1. Tony Stark is Riggs
"I am Iron Man." That's the last line Stark leaves us with when the movie ends and we get it; with or without the suit, with or without the arc reactor Tony Stark is Iron Man. However, in Iron Man 3, Stark is really Martin Riggs for a few reasons... He's haunted by the events in New York just like Riggs is haunted by the death of his wife; he can't sleep, is always on edge and the only thing Stark really cares about is Pepper's safety. Stark is incredibly reckless, even more so in Iron Man 3. Who the hell gives their home address on live television, inviting his enemy to come and take a free shot? I can think of one other character. How does he deal with his demons? SPOILER ALERT... Stark gets Pepper back, killing Killian and all the Extremis agents in a blaze of glory, then destroys his Iron Man legion. Only then is he free to move on with his life and get rid of the shrapnel in his heart; when Stark threw the arc reactor in the ocean in the end of the film, it was parallel to Riggs giving Murtaugh that hollow point bullet. Both got rid of something they were dependent on for a long time, and experienced a change of heart. For Tony, it was more literal; as Riggs found his reason to live at the end of Lethal Weapon, Stark found that he was more than the reactor or the suit it powered, he was Iron Man. If LW5 was greenlit, Black would've brought the franchise full circle and brought back many of the original elements and themes back, but since it wasn't Iron Man 3 became a natural vehicle to get LW5 out of his system. Whether intentional or not, one can't help but notice the similarities between characters and situations between the Iron Man and Lethal Weapon franchises. To put it in simple mathematics: (IM3 - Stark and Rhodes = LW5 + Riggs and Murtaugh) / Shane Black.