It’s been a while since I’ve seen a discussion on the topic, but as of a few years ago, Blizzard was interpreting the TOS to ban client-side model injection. Suspensions and all, even if it were being done for benign cosmetic reasons.
Note the use of the word “client”. Once upon a time, players assumed that the TOS prevented modifications to game files, but in-memory data was free game. Turns out, Blizzard considers the memory-resident parts of the game also protected, so a dynamic model injector will also violate TOS.