This tangent is getting pretty off topic, but whatever, it's probably more interesting than whatever the topic actually was.

we could prove agency in theory.
It's a bit cyclical-- quantum probability (if that's a phrase) is being posited as a potential source of freewill. If you need to reach outside of the quarks doing quirky things to say that some other phenomenon is influencing the probability of which quirky thing they do, well, you now are saying that freewill is not born of the quarky quirks, but instead just influences them. That puts you squarely back in square one.