Some ideas.
Not sure what books you have or what is allowed, but I had fun building a Force Missile Mage/Argent Savant with Arcane Thesis and Spell Thematics.
+3 Caster Level on Magic Missile with 2 extra missiles, +1 extra damage per dice, auto still/silent with any element. Quicken spell for additional fun since it's only a 1st level spell and arcane thesis lowers the adjustment to +3.
There is no save for magic missile and casting at least 3 levels above (other feats can help too) helps bypass SR. Plus you can potentially bypass sheild spells and the like. If you're going to high enough levels, Mystic allows you to permanently affect one spell with empower, extend, quicken, and maximize, but that will take you past epic I'm sure.
Otherwise, depending on the level you want to reach...
Initiate of the Sevenfold Veil is very powerful for an abjuration specialist and is different enough that you might have fun. It's difficult to get into and doesn't start till at least level 10, but the payoff is worth it in my humble opinion. You can even master specialize in abjuration and cast buffs and dispel magic to your heart's content.
Finally, depending on how you run polymorph...
You can get into some of the polymorph classes like Master Transmogrifist and Warshaper "early" by taking the prestige class "Shaper of Form". I believe they get a polymorph at level 2 of the class (potentially level 7). Offset your low BAB with some Fighter or Barbarian levels and you'll get a half dragon/half hydra with bonuses to hit and damage.
And if none of these thrill you, there's always factotum/wizard/mindbender/exemplar for the skill and charm/dominate expert. You have to have a non-good alignment, but permenantly charming the dragon and picking up the leadership feat might be fun.