The “how many planks can you replace in a boat before it’s not the same boat anymore” puzzle, except “how many mods can you install on Skyrim before you’re not playing Skyrim anymore”
The Skyrim of Theseus is my favorite philosophical quandary.
Fun fact: you can play the entirety of Fallout 3 inside a mod of New Vegas. It’s called A Tale of Two Wastelands and it’s the best way to play Fallout 3.