Just a quick question...
Assume a powerful White Court Vampire. He has Supernatural Speed and Toughness, with the usual catches.
Our resident vampire wants to impress some mortals in a meaningless contest -- showing off at basketball, or something equally low-end that doesn't require his full capability.
Would you allow the character to use the "Inhuman Speed" (and it's resulting Hunger Stress) instead of going all-out with his full Supernatural Speed (and the higher Hunger Stress)?
The only relevant section in the rules (that I have found) is the side-bar on YS190: "Some GM's might allow certain abilities to “downgrade” as they absorb hunger stress, so Supernatural Toughness might become Inhuman with a 2-stress hit."
I could see allowing this for characters, since higher-level abilities automatically replace the lower-level powers. It gives a player a bit more choice, in determining how 'all-out' his character feels the need to go in different situations. A player asked me about at our last game and I didn't see any real problem with it... but I thought I'd come here and see if anyone else could find an issue or potential abuse I had overlooked.