One BIG feature would be having the avatars meshes totally redone, with a clean, homogen UV mapping, and clean joint deformers. Seeing what the most recent SL competitors made in terms of avatar graphics, I even think its an imperative move if we want to stay in the run.
A new, improved avatar could live together with the original one, for a certain amount of time, to allow everyone time to adapt, I particularly think of clothing and skin makers.
Also, wearable flexi sculpties, that actually follow the avatars rigging would be nice. Make a sculptie piece of clothing, wear it, it follows your bones rotations.
I definetly think if this is not done quickly, we are in serious trouble when it comes to seduce new residents, if they ever take a look at what sony does....