> To configure them they must be supported by compositor. Userspace tools can no longer switch/move/rotate monitors.
Isn't the compositor a userspace tool? Can't it expose an interface for a command line tool if desired, maybe even have that interface standardized (such as via D-BUS). Doesn't the window manager/compositor have to participate at a fairly low level for R-and-R events anyway? I don't see this as something that's going to be a big change. The window manager/compositor already does mediate pretty much everything, with the existing X system being a giant wart on the side to be worked around.