Or require a discipline check against the threshold to change form - one or the other. A shapeshifter that explicitly turned into a real, physical, ordinary wolf wouldn't have their physical abilities reduced at all, though.
I don't know. It depends on how they are turning. Turning into something bigger might require the use of ectoplasm and that is harder to access through a threshold. Billy uses magic and it might be harder to control his form if the magic is more tenuous.
And just because you scratch 'claws' off your character sheet, it doesn't mean the wolf form in the story has no claws. It just means he's less able to use them as effectively because the threshold is somehow impeding him.
I do like the idea of a discipline check to change form. You could even do that each exchange to maintain their form.
I'm not sure there's a right answer. There's lots of ways to do it. A compel to prevent them from shifting could work too.
