The implications of soul-based magic already sounds interesting. Especially if your actions in-game actually affect your characters soul, changing the intricacies and options of your spells. The type of magic you perform can take on all sorts of different colors, according to how your story plays out and what kind of person you become.
But what do you guys think about a psionic class? Perhaps there are people in the world who reject the philosophies behind soul-based magic, and turn to cerebral-based magic. I loved Dakkon being themed as a psionic, but it kind of sucked that he basically played just like a normal mage. In Eternity, a psionic could explore an interesting niche of play, being casters of an unusual sort that might rely more on personal augmenting magic and doesn't suffer from effects that normally disprupt soul-based magic.
Perhaps they could even function as anti-mages, having a sort of affinity for taking out soul-casters? They could be silencers, disruptors, have high resistances against magic, and maybe even become empowered by dispelling/destroying soul-based magic. I remember in a 3rd Edition D&D book, Masters of the Wild, there was a class called Forsaker who basically denounced all magic and gained all these neat powers when he destroyed magic items. I loved the idea of the class, even though it was poorly designed for party-friendly play. It also reminds me of the Wizard Slayer kit from BG. What if psionicist worked in a similar way? They can't use any magic items, and gain interesting abilities by destroying them?
Psionics are so underused in RPG's these days. Why not give it a try?