Uhm... definitely no. I was thinking the flesh items would come from 3rd party 'victims' that you can use as ingredients. You just keep them in the inventory when you use your powers and they will be 'spent' for what ever purposes you are attempting to do. BTW: The subject does NOT get the choice, the caster gets to choose what stat is sacrificed. I was not thinking about 'scrolls' of any kind.
Other notes:
The soak is not coming from stamina. That wasn't stated, but is open to the ST, granted the book never said anything about raising stamina as the source of soak. Stamina isn't just for soaking, it's also a physical endurance stat. If you're altering the body tissue to enhance the limbs in some way, I totally see this affecting stamina - especially if the subject is mortal. For dexterity, the player can loose balance if they are doing alterations to their legs. This can offset their balance in equilibrium till they adjust to the change (spend exp to regain dexterity). This can also affect dexterity if they are altering the fingers on the hand or the whole hand as well especially if the alteration is to enhance the strength of the hands. Thus end up sacrificing dexterity for strength, especially when the subject needs to do precise finger tasks (picking a lock or trying to use a bow and arrow). So overall, this power can be used to do more than just raise "soak".
The amount of things you can do with this power leaves the core book much to be desired with its lack of explanation. You really have to think outside of the core book, man, because the core book really is not the end all of explanations. Actually quite the contrary. Especially when the book describes Vicissitude.