This is an incredible achievement, and despite it being far outside of my area I was fascinated by it.
Seems like the strided accesses to the EFB could be recognized in the JIT maybe, and only the pixels likely to be accessed would be copied (not sure how they prepare the EFB copy though, maybe they're not able to resample it).
Superb and very enjoyable writeup!
The kind that makes you sit down in a comfy chair with a cup of hot chocolate and enjoy a good read.