Here's another of one of my ideas for W101 that probably won't get added, but it would be cool to see. I'd think it would be cool if Wizards could promote to a new class. I could have sworn I've seen another post like this in the past though...
Tactiton: Tactions are a master of teamwork. They make great leaders and are great at putting on traps, blades, and what not. As for attacks, they are more typically balance spells, but don't do as much damage on their own. They also make decent healers. Promotion for Balance Wizards.
Elementalist: Elementalists focus on attacking with all the elemental (Fire, Ice, Storm) magic. Promotion for Balance Wizards as well as Fire, Ice, and Storm Wizards. Whether they are more defensive or offensive depends on the type of school they were before.
Spiritualist: The sister class to Elementalists, except it attacks with Spiritual magic. Promotion for Balance Wizards as well as Life, Death, and Myth Wizards.
Exorcist: Excorcists are masters of summoning monsters of their own will and invoking fear in the enemies. They hit hard. Promotion for Myth and Death Wizards.
Distortionist: Basically the sister class to Exorcists, except instead of invoking fear with death, they decieve with life. They don't hit as hard but have higher accuracy. Promotion for Myth and Life Wizards.
Shaman: Shamen are dark healers and Wizards from the darkest parts of Nature. They can heal, but also take health from their enemies. They don't hit as hard as Exorcists, but they have better accuracy and defense. Promotion for Life and Death Wizards.
And then there are just the basic "Great Conjurer" or "Great Necromancer" classes that are just slighty upgraded versions of their current school. Unfortunately I don't have any ideas for other Storm/Ice/Fire promotions, but hopefully they'll do. Feel free to leave input and other ideas if you want.