Becoming animals class is named "Morphist", not "Summoner". The simple concept of Summoner/Evoker is to summon something to help you ^^:

The idea is valid, but the class isn't. We do can have more than one class dealing with avatars though...maybe a "Vessel" class that can be possessed by an avatar...it would be mainly the very same difference between beastmaster and morphist...one charms the monster to aid while the other transforms into the monster.