While it may not be 20th level Wizard casting, I find that Wizard 6/Warblade 1/Jade Phoenix Mage 4/Abjurant Champion 5/Shadowcraft Mage 4 works wonders in any campaign. Focused Specialist (Illusion or Conjuration) banning Enchantment, Necromancy, and Evocation is recomended to make up for lost spells. BAB +18, casts as an 18th level Wizard, and can pull Shadow Miracles out of his ass.