Definitely a workable concept. In fact, for the Hulk you'd probably want to change Human Form [+1] to Human Form (Involuntary Change) [+2], and add Hulking Size [-2]. So:
+2 Human Form (Involuntary Change)
*-1 Beast Change
*-2 Hulking Form
*-4 Supernatural Strength
*-4 Supernatural Toughness
=
9 Refresh
As to the Catch ... I'm not sure that the Hulk really had a physical weakness. Perhaps you might tweak the system to allow for a mental weakness? For example, perhaps he can be manipulated via his anger, allowing opponents to tag one or several appropriate Aspects for free, when trying to manipulate him? Or perhaps a trigger that causes his rage to ebb, thus reverting him back to Human Form?
Edit: Oh, and as to justification in the Dresdenverse for this character ... perhaps the character got pissed of at a power Winter Sidhe and was very rude ... and the Sidhe cursed him to forever wear his anger as a change to his form, basically turning him into what for a lack of a better term I will call a Were-Troll.