Hey there, I recently posted something about Stamina consuption in Corrupted Builds. With that said, my post is mostly about Corruption in general, not Sorcery.
Anyways, to meld a bit of what I said with what you did:
What you mentioned about the part of Stamina that’s Corrupted being usable as some other form of battle resource could be interesting. Perhaps the more Corrupted you are, the more damage your offensive Sorceries could do? For the status based Sorceries (like Slow-Fall) the durations could be raised? Maybe cast time could be hastened by further corrupting?
Just a few system-orientated ideas there.