causing an app to crash because it tries to do a screenshot and it wasn't allowed to seems like a very reasonable thing to have happen :-)
While I expect that doing checks on these half dozen or so 'special' priviledges would break a few things, I don't think it would be that many, and if the capaibility was available, distros would experiment with them.
After all, we know that SELinux breaks things, but it's being deployed. I would expect that SELinux has broken far more things than a handful of permission checks in X would.
> The point of the presentation wasn't to fix X, it was to fix DRM
this writeup makes it sound like it was talking about problems in X not in the DRM layer.