Hi Sam! It sounds great! :D
Actually, raylib gestures system only requires some touch events to calculate gestures... probably UWP already offers a similar API to detect gestures directly, instead of just raw touches.
Current raylib timming implementation is based on GLFW3 on desktop platforms and custom on other systems, UWP should use their own... despite that probably, it is fixed by default internally to 60 fps (same on Android).
Just found
this useful reference, to see which Windows libraries are available on UWP.
Looking a bit further, noticed that
QueryPerformanceCounter is available for UWP, so it can be used for timming, great!
About storage, yes, I mean file I/O, many platforms usually provide a Storage class to access file data in a controlled way, just found
more info here.
With those points, I think mostly all raylib functionality would be available on UWP! :D