Edit: That is peculiar. The game is unlikely to work successfully without the mainmenu.gd file in the mods/aricsexpansion/scripts as that has a lot of the main functions and there isn't one in the "Important" folder (besides the mainmenu.scn which is different). When you load up the game with the mod, are you no longer getting any errors? And do you see the new player specialties (Breeder) or starting slave hobbies (Waifu, perfect specimen, etc) or vagina/ass sizes?
Viewing post in Aric's Expansion Rebred
No Errors on loading the game with mod installed and that specific file removed, but I cannot see the new player specialties or slave specialty classes, but I can see the traits like 'stutter, lisp, lactating' and I can see the sizes of vagina/ass/balls etc. only once I'm actually in-game, not in the new game menu.
Edit: So somehow, upon doing the exact same thing I've been doing (with the only difference this time being keeping EVERY window open so I can watch all files get replaced and when) the game is working perfectly? I'll update if anything is broken upon further play.
Edit 2: Trying to use an old save that had partially upgraded the farm, the farm store, snails, and vats are inaccessible. Attempting to rush through a new game and unlock them to see if that is the case there.