Thought some more, and I have some ideas.
One of the realizations I think I had is that magic recognizes divisions where there are none. PT being the prime example, but also the ability of armor to block spells. PT relies on removing the caster’s understanding of divisions; what if there is a way to add divisions? If Harry can convince himself that his skin is not part of himself, will it block spells the way thick leather does?
Conversely, are there other divisions that open possibilities if removed? Like between people and the ground, or people and people?
Most thinking I’m reading about uses PT to create a weapon with which to attack, but attack is not the goal. Escape is. Means of escape fall into a few categories, I think: Figuring out something like Apparition on the spot, quantum tunnelling, or Newtonian. Right now I’m just going to think about “newtonian”—It’s just as ridiculous for transfiguration to not include velocity as it is for it to only effect “discrete” objects. Can Harry simply add enough velocity to himself to escape? (Adding acceralation doesn’t work, as enough to escape fast enough probably squishes him)
Here are crazier things:
There’s good proper acausality in this universe. Coma-tea, time-turners, and the Stars spell. What’s going on there? Is there some way to use that?
At first, there is evidence that changes to the body and brain effect the mind. But, there’s also a pile of evidence that, under circumstances, it doesn’t—Horcurxes, and both resurrections. What if Harry can detach his life/magic from his body?
So, release of magic doesn’t require movement. That’s something.