the animations are tied to the model…the old models getting the new animations was a bandaid on live because of certain spells(monks), they ended up gettign rid of it after starting the new class animations because all the detail did not work on the old models and caused problems, but because classic is based on the old animations the new old animations on the new models will match the the old models with the old aniamtions.
plenty of private servers have new model patches, it would not be hard to add a toggle as all it would be is the toggle would change the target files of what to display locally.