You can do this with X, using a utility like
Xvfb,
Xephyr, or even a
VNC server.
It works similarly to rdpwrap, but doesn't require distinct user accounts or hacks that circumvent the limitations of the OS ;) Xvfb is very light on resources as well. Presumably Xephyr is a bit heavier and running VNC servers will cause significantly more resource consumption but can be useful for remote control.
A few proof-of-concepts exist, see
here for a (very simple) example of how I made Simba run the necessary programs. This should have been done with Xlib but I got lazy and had Simba make system calls using TProcess instead. When coupled with SRL's more proper Xlib integration, this could be a cheap way to programmatically spawn RuneScape bots inside fake X displays.
Something like this was also used as a component of BenLand100's
Python macroing solution.