While I’m not employed at Invisible Things Lab and can’t speak on behalf of the company, I suppose this will be the case in the final release, i.e. sys-gui-gpu having some ability to interact with dom0 via well-crafted policies.
If you have more spare time than me, you can play around with them and write your own ones, contributing to the system development. Any would count, even as simple as one that lets a user gracefully shutdown their machine (right now there’s only a forced shutdown available through holding down the power button).
Last month I also published a list of what works and what does not after experimenting on my own.