A wizard or witch with an animal familiar can upgrade it once 3rd level is attained to a Celestial or Fiendish animal version by taking the feat Improved Familiar. However, at higher levels such a familiar lags behind the Improved Familiars that become available at 7th level. In theory, such a PC could simply swap out for a Cassissian or something and of course wizards with raven familiars could swap out for Nosoi and wizards with cats could take Silvanshees and retain flavor. What, though, would be an appropriate 7th level powers upgrade for a celestial hawk?
Does anyone have any suggestions?