ppsspp has the source code but it doesn't have the modern UWP user interface. Don't know if it can pass the store auto-cert procs.
On the other hand, vba10 works quite handy.
Other than some gamepad bugs on Xbox One(like adding and select the rom, switch back to mouse mode might work, but...
as a c# and xaml dev, cpp is just rocket science to me. But I'm happy to compile and distribute it free on store.
p.s. I have experience of adaptive UI and xaml