Well that would depend on what type of character you want.. Buff mage, Dual-caster, or Companion Buffer (The arcane Heirophant's companion familiar can get fairly powerful)
For example, with your listed progression, you would be an equivalent 23 wizard caster/27 Druid Caster with 27 levels of wild shape and the animal companion of a 27th level druid with all of the familiar abilities. It pretty much comes down to what kind of style you want to go for.
One amusing side bar: If you decide to go with the companion route, I might suggest checking out the Beast Master from complete adventurer, not a caster but gets some good beast buffs, and multiple companions.