A few suggestions. One, I'll agree with Velenne that the PC casting classes are a little underpowered for a dragon; the PrCs in the Draconomicon offer much better progressions if you can reach them, as they offer full BAB, multiple strong saves, and no hit die smaller than a d8. Though it would take you until 25th level to qualify, the Elemental Master is also a really, really nice choice. Otherwise, dragon hit dice seem the way to go; 2/3 casting progression, but much better combat potential.
Spell Penetration is going to do you exactly zero good; there isn't a single truly epic nasty with SR low enough for a +8 to penetrate. Metabreath feats may be more useful, especially Clinging Breath, Empower Breath, Ability Focus: Breath Weapon, and the all-important Rapid Breath. Leadership could give you either arcane backup or, with the Dragonrider prestige class, a number of extremely useful benefits (better maneuverability and Flyby Attack).
For items, an item of natural armor would boost your AC into the nigh-invulnerable range. Claws of the Ripper would make your damage potential truly awesome, especially in conjunction with a keen enhancement on the amulet of natural weapons ( payable by dropping the flaming burst down to flaming).
And one more thing; you can't make Draconic Might permanent. Bonuses have their own formulae, and an item of Draconic Might would cost 182,000 (25,000 for each +5 to an ability, 32,000 for the +4 to natural armor, and doubling all but the most expensive for being one item).
