About the potion power, what about creatures that are simply immortal (physical immunity) or would not be subject to poisons? (such as living dead). Can they drink your potions and take benefits without having that power?
I suggest that, without the power to adapt to the potions, the potions not only kill you but also have no benefit; it is your body's adaptation that produces the effect.
Also, no potions for clearing mental stress please. Especially since the character would be casting spells with mental stress cost. Effectively you'd be trading one "Toxicity" box for three spells cast.
The power states only those with the power get the benefits, since they are slightly immune, which comes partly from constant exposure. While someone with Physical Immunity wouldn't die from it, they might still get sick as a dog (Nicodemus puking his guts out and peeing blood would be a good situation
). And Living Dead don't have digestive systems, they aren't getting any benefits from it.
I understand the no Mental Stress recuperation. I'll make Tawny Owl provide a temporary Athletics boost.
Tbora, it might be harder for a wizard to make some of these potions, but:
1. They can't be shared (unless the recipient has the same power).
2. They can't be over-used (on penalty of death/hospitalization).
3. It gives no other kind of Power. You can't spend a single Refresh to turn it into full Thaumaturgy. It is stand-alone.