I got an idea today. Instead of building a kiosk mode for foobar2000 itself, why not use Mozilla Firefox in kiosk mode, together with a Firefox extension like Foxytunes?
If Firefox extensions for kiosk mode do not work well with Foxytunes, (I haven't tried this myself,) would it be possible to build a new Firefox extension for running foobar2000 in kiosk mode? If yes, would it be feasible as well?
I'm not sure if this is a good idea, but I would pleased if people could add to this idea to make stuff work.