It’s just me or RetroArch developed the best FLOSS alternative to proprietary UI? You have a nice overlay, CRT shaders, bezels, some netplay function, customizable interface. All of this completely free and super fast.
Wouldn’t be nice to also launch non-emulated games from here?
A lot of what you list is built into the emulation cores and are not just UI features.
For games that don’t use their emulation cores:
Basically they would be building all the tough bits from scratch to do everything you’re suggesting