Recently had this idea, and considering how RVGL is stabilished nowadays, i think it would be doable.
Would it be possible to make it a LibRetro module in the far-future? Considering its basically its own thing now, if done similar to other sourceport cores (like Quake, DOOM, DOSBox, etc), it could work just fine.
+ support for stuff like shader overalys, changing shortcut options by restarting the code, using and changing INI stuff via the RetroArch options, would be pretty neat.
Post suggestions regarding RVGL.