Alright, here is the build:
Human Wizard 5 (Spontaneous Divinations ACF)/Red Wizard 5/Dragon Disciple 10.
All you need are the pre-req feats, and 3 Innate Spell feats taken at 12th, 15th, and 18th levels. I suggest Embrace the Dark Chaos, Shun the Dark Chaos, and Shapechange, for starters.
How does this work? Dragon Disciple gives you bonus spell slots of any level that you can cast, your choice.
Circle Magic allows you to cast 20th level spells (Thank you, free Heightening!)
So therefor, you can grab 20th level spell slots.
Now, what to use them for? Metamagic, Reserve Feats, Arcane Transformation, Draconic Feats (a 40d8 breath weapon would be brutal; or a +20 to saves for one round, to really save your hide.)
Or, my favorite, Innate Spell; it gives you the ability to use a single spell at-will, once per round, as a SLA (iirc, you still need to supply the material costs and experience). However, it costs you a spell slot 8 levels higher than the spell you want at will.
This is no problem here.
Once you get at-Will Embrace/Shun the Dark Chaos, use all the bonus feats you have undoubtedly collected to give yourself some more Innate Spells. And some Extra Spell Slots, so that you have more room for Innate Spells.
Any nitpicks anyone can see?