Im not much for casters and havnt critiqued any PrCs as of yet but id say this is really good. I know of a certain pyro wizard in my party that would jump on this in a heartbeat.
That said, i cant shake the feeling that your missing something.
Ah, now i remember. Since all of your damage dealing spells could essentially be narrowed down to either fire/cold or a handful of others (like disintegrate), shouldnt you throw in some ability to ignore or reduce damage resistance/immunity to your element? It seems rather pointless to be a Mage of the Fiery Soul fighting a Red Dragon and still have to rely on magic items to overcome its defence to your most focused and possibly reliable damage output.