Much depends on what animal you turn into. If you're playing the type of Were-Form that just changes into a real-life animal that can soak up a lot of punishment, I think it'd make sense to just have the catch be anything above a certain weapon rating. I think I'd also add some restrictions, such as no Toughness powers unless your animal has Hulking Size or really thick scales or the like. Now if your wereform is, say, a White Wolf style garou, then you'd take the toughness power and give it some kind of magical catch.