Need critique on a new ability (Animal-Shifter)

[Zealot Vedas]

So, I'm kicking around an idea for an Animal-Shifter ability, to let you transform into various creatures. I'm envisioning it as being similar to Gear and Magic (Arcane) in that it gives you access to bonuses, but with a built-in drawback.

Gear has the drawback of being able to lose the items that give you the bonuses, and Magic costs endurance and has a chance of failure. I was thinking that Animal-Shifter might take multiple rounds to activate, and maybe giving a penalty to actions the form you have taken is unsuited to.

For example, let's say a character has
Animal-Shifting +4
Rhinoceros +4
Black Bear +3
Harpy Eagle +2

If that character wanted to transform into a bear, it would take 3 turn to transform, and he'd get a +3 bonus on rolls for things a bear would be good at (Mauling someone, catching fish and such), and a -3 on things a bear is unsuited for (Making a speech, dancing ballet).

Returning to your true form just takes one turn. Considering allowing a character to spend endurance to accelerate transformation; maybe (Level of animal form)x5 to make transformation instant.

Thoughts and critiques?

[Malancthon]

I'd probably approach it using Shape-Shifter level 4, and then use a Weakness to limit the forms to animals only. I imagine it'd be a -2 Weakness to limit to animal forms.

Taking a look over at Shape-Shifter, the forms do not give any mechanical bonuses, so it's implied you can just do things. One of the more abstract things about OVA is that levels for Abilities such as Flight and such don't give you actual speeds, but instead you move at either a plausible speed and the levels in Flight only describe how nimble you are. Superboy and Superman both fly faster than a speeding bullet, but Superboy only has a +1 bonus for flying (Flight level 1) while Superman is more experienced and flies better (Flight level 3+).

So, going back to Shape-Shifter, I'd use Scale bonus. If you turn into a bird, you innately have Flight and get the Scale +5 for using that natural ability. Likewise, being a bear might give you a Scale +5 for strength.

[Clay]

Another avenue for something like this is to take Transformation and use Human Arsenal (rename it something fanciful like "Hundred Spirits" or whatever) to allow you to create any number of permutations you want. In this way, you can define more exactly what each animal can and can't do.