I don't think that would work to be honest. Shasha would recognise Leon's a wolf yes, but it has been mentioned before that whoever is trying to get people to impersonate Leon was getting closer and closer to what he looks like physically and personality wise. The form she remembers was when his fur was fully white as well as him being a timid, little fluffball who loves being around her and is too weak/innocent to defend himself. If he were to transforms now, he'd have a confident stance and flack fur, which would be the opposite of how Shasha remembers him to be.
I belive the only way to identify who the real person in a room full of impersonators is is when you're able to anwer questions that only the interrogator and interrogated can answer, like the pee example I mentioned in the previous comment.