I’d propose to add a power and sleep button to the UI (e.g. top toolbar, or toolbox where the other shortcuts are) and send these as USB key commands to the host. This would allow shutting down / standby the host without clicking around in the UI.
What I found annoying is that when trying to stand-by my host (Windows): when clicking on stand-by in the start menu, and then moving my mouse away after clicking, the mouse movement would immediately wake up my host again. This could be avoided by having a way to stand-by the machine without clicking in the host’s display.