could you define magically treated? do you mean just any magic item?
If it is just any magic item, then asking for a trait to allow none magical items the same effect is not asking much as far as game balance gos, as it would be easy to cheese this requirement by using once per year level zero spells on items, 49 CP per item :/ or even just giving use affect to be less cheesy for 12.5 gp and then just not using it unless it is absolutely necessary. my point is, the only time letting magical gear mend into animal form is a mathematical combat advantage is at low levels before a martial class has magical weapon(s) and armor, after that point, all you're doing is making racial trait, the trait that makes a Nai-nek-chai a Nai-nek-chai, used less often.
[Also, note that my character will have the spirit subtype ;3]
That said, if it needs a special magical affect, how much dos it cost? if we're talking just a few GP per item, a trait is still plenty, keeping in mind that one trait gives hundreds of extra GP at level one, and the usefulness of being able to mend non magical items can decay away rapidly.
and as for using two traits for it while saying a feat would simply be too much, I have to say the same to that, a trait is worth half a feat, thus two is basically a feat. (in fact, there is a feat that gives two more traits)
Also, are flaws allowed? :/