Anything else that's weapon 2, you wouldn't spend Refresh on.
Claws is mostly analogous to Fists stunts like Lethal Weapon.
And Orladdin, your argument doesn't hold up. Human Guise is free. Human Form is cheaper than free. (Incidentally, the fact that Claws + Human Form is better than Claws alone annoys me.) And even when people don't have to look weird, they often do. Because looking weird is only a problem if the GM tosses you a compel, and that's free FP.
I can't overemphasize how important that principle is. In order to make it mechanically okay to make weird narrative decisions, you need to punish those decisions with and only with compels.
Otherwise you run into a few problems. One is the lack of granularity that Orladdin mentioned. Another is less freedom for character-makers. And yet another is a lack of interesting stuff like the nasty bat forms of RCVs.
Incidentally, saying that Claws is always visible makes it hard to simulate a number of things other than super punches. Like retractable claws, for instance. Sure, Human Guise works, but then your character gets unexplained impulse control issues.
I worry that you might be starting from the conclusion that the rules are OK and then trying to justify them. Think about it this way: if you were writing the game, would you add that restriction? If so, why?