ABSOLUTELY could cause turmoil in the pipeline. New shape keys and altering existing will require new PCA to be ran and all animation could very well break. Not much use in film because of this (I did see some comments of feature films using this in a different way, but I think that is more of an early 2000s mindset when PCs would stall with 200+ shape keys on advanced rigs). But yeah everything you are saying is on point I’m glad people can follow and I’m not just going insane.