Question about elemental animals

How would you go about giving magical animals elemental forms such as those in the inner Bjornaer mysteries?

Say there was a shadow cat or a fire hawk or an ice horse?

The MuAn guidelines say base 15 to change an animal in a major unnatural way and 25 to radically change an animal in an unnatural way... I'm tending towards the higher base here as it also works for giving "an animal a magical ability".

So tentatively:

The Elemental Beast MuAn(Prereq) 40
R: Touch, D: Sun, T: Ind
This spell or power turns an animal into a version of its species made entirely of the element or form used as a pre-requisite. A Pre-requisite in Terram for instance might create an earth, sand or stone (+1 Magnitude required) version of the animal.
(Base 25, +1 Touch, +2 Sun)

Would that work or is there need for a Rego requisite (keep the element in "shape", so to speak) or +1 Magnitude for complexity?