Mounts are a great idea for traveling the different worlds. I love the speed aspect, but sometimes I just want speed and no mount at all. I'd like to see shoes or shoes/Mounts with 40% or 50% speed.
Designing gear would be awesome. Let wizards design every aspect of certain gear bundles. Deciding how small or big of a hat. Does robe come with a cape. Is that cape long or short. Maybe Spikes for shoulders. Etc.
Personalizing wing Mounts per school that a wizard is in. Fire school would have wings in engulfed in flames. Storm school would have electric wings, etc.
