[incubus66]

Avengers Endgame is a good movie but the infamous scene of the rat saving ant-man from the machine could be a thing much more emotional, Stan Lee is died when the movie is coming from the theather they could replace the rat with a "Stan Lee" look alike 
imagine ant-man tell to the man "what is your name" and the old-man talk "'Stan Lee" and ant-man look to the screen hug him and say "you are my hero" is a very emotional scene.

[Akaino1999]

While it could be done with a Stan Lee cameo, in my honest opinion the improbability of the rat scene happening adds a lot to the film. It creates the joke that the fate of the universe rested in the hands of a rat, but also makes the watcher think "Hey, were there possibilities where Iron man could have survived if someone else hit the button?"

[Omega Samurai]

I would have been cool if they like added the rat to some scene in infinity war or antman 2, but I know they were still figuring it all out as they went.