FileBot

I was previously using my own python script to handle all of this and decided to give amc a go. I was able to get it to do exactly what I want except for one aspect. I have it set to --conflict override which will overwrite the file if the same exact one exists already. I need it to check if the file already exists under any other extension as well (.mkv, .mp4, .avi) and if it the new file is a .mp4, but a .mkv already exists, delete the .mkv and then move the .mp4 over.

Does AMC already have this functionality? If not is this something that can be added?

This is not supported, and is not planned.

However, it's easy to find movie/episode duplicates easily later on, based on name or xattr.