Originally Posted by
AslanCross
If you really want to use fire without being gimped by immunities, might I suggest the Silver Flame Pyromancer from Five Nations (Eberron book). You could easily refluff it for the flavor and the alignment restriction. Its main class feature is being able to convert any fire spells into sacred damage (half sacred at first, then once you hit level 4, full sacred damage).
It does suffer the loss of a few caster levels (and you have to multiclass as cleric), but taking Practiced Spellcaster solves your Arcane CL problems. Also, you automatically add Paladin spells to your spellbook for some odd, awesome reason.
It's only 5 levels long, so you're free to PrC elsewhere. I made an 18th level Wizard/Cleric/Fatespinner/SFP once. He blew stuff up without even taking Practiced Spellcaster. Maximized Sacred Orb of Fire = win.