All 3.0/3.5 books are allowed and the DM is allowing us freedom to choose any class and ignore some prerequisites and other requirements. I'll gain minor innate spell casting like plant growth and detect evil as well as some spell like abilities at older ages, increases to the breath weapon as well as damage bonuses and AC bonuses as we age and grow in size.
So basically, I have freedom to choose any class, I have a breath weapon that will increase in damage as I level up as well as natural attacks that will increase as I level. I can also fly, so I'm wondering, since I have natural attacks and natural armor, would a spellcaster be the best way to go? Or should I go for a fighter and just pump him full of feats that will improve natural attack damage, breath weapon damage and stuff like "fly-by attack"?