I'd keep the sorceror as a class but focus more on the bloodline, with less vancian magic. I'd like the bloodline to be more then just arcane spells or powers, but actual incremental apothesis. So you'd get some spells and powers, but more importantly you'd be slowly evovling into something. Like if you picked dragon bloodline, piece by piece you'd be evovling into a dragon of your choice, so by high level play, so are a dragon, with an ability to take on a verson of your mortal form.
If you take the the infernal bloodline, in time you actually become a unique devil.
If you take elemental bloodline you become an elemental, trait by trait.