Updated Graphics would be nice, but I would at least like Blizzard to update the original game engine. Even with today's hardware you can't avoid framerate dips on a 10 year old game when maxed out, no v-sync.(1070, 7700HQ) God-forbid you increase certain graphical settings through the console. This experience being from well-known private servers.
If people's idea of an authentic experience is playing 720p at 30fps, then you can get a 2006 computer for your 2006 experience. I'm okay with 2006 textures/models/shaders/lighting/animations. Updating those would be great, but I can see those taking away some of the vanilla experience from some folks.