This is a slightly odd question, since most of the requirements
can be done using an event synthesizer, but it's an interesting
hole in Xvfb. Is there a plan to put a pipe and/or a socket
communications method in Xvfb so that I can emulate a display
complete with keystrokes? Or do I need to look elsewhere.

(My application can't use Xnest; I want to take the raster and
map it into a GL texture buffer, for some interesting 3-D effects.
I can move the cursor using XWarpPointer, so that's covered.)

It's still legal to go .sigless.