Joss Whedon had commented that he shot a scene for Age of Ultron to accommodate the presence of Carol Danvers at the end of the movie. Apparently, it was never going to happen because Kevin Feige wasn't fond of the idea of introducing her fully formed like that at the end of the movie. Here is a shot of the scene with Carol's stand in, to be replaced digitally once the character was cast.
https://comicbook.com/marvel/amp/2019/11/16/marvel-avengers-age-of-ultron-captain-marvel-scene/
I also remember Whedon stating that they shot an alternate ending with Quicksilver, just in case someone at the studio didn't like killing him off. I would like to see that shot as well.