I would opt to fix bugs, and potentially add autoloot, since (1) bugs are annoying and (2) autoloot doesn't affect gameplay or imo nostalgia. Whereas character models or NPC mechanics or game functions will affect my memories.
Either way - Keep it the same as original. I do fear once Blizzard changes one thing they tend to change 10 or 20 other things under the same internal memo, break stuff, repair it and the end result is never the same.