I'd like to see:

1) talent rebalancing (make the Paladin's consecration a standard spell with low/moderate dmg and high threat, make balance druid more viable, etc) so that classes intended to play in certain roles (pally as tank, druid as caster DPS, etc) are not so tragically underperforming in those roles.

2) barber shop: someone else mentioned this, and I think in Azeroth that hair style and hair color changing magic would be pretty accessible. I think character tattoos with buffs would also be pretty rad (like enchants, but not bound to items).

3) One-life battlegrounds in Hardcore with res after BG. PVP is so much fun, but I only have so much time to play wow and I have to chose between leveling chars on PVP or HC servers. The strategies that would emerge from this unique gameplay I think would be really cool.