No current project like Retroarch, Dolphin or ePSXe will be porting its emulator to UWP because Microsoft has recently changed its policies and is eliminating all emulators from its official store (Windows Store). Installing .APPX applications from outside the official store is more tedious than traditional Win32 programs that are easier to install and people are more accustomed to them.
In fact Henrik, developer of the PSP emulator PPSSPP, ported a version to UWP after many users bothered him to do so. Dolphin's already said no. Those of ePSXe are a mystery, too many secrets, surely have something to hide from your code as I said before. The fact that the plugins of other free emulators work is very suspicious
Honestly the best thing you can do is try to port projects to UWP like Retroarch, although I personally prefer emulators that are dedicated exclusively to emulate a system. Emulators that cover a lot do not tighten.
I'm sorry to be a troll to some users, I just tried to be clear and open my eyes on the complexity of some projects. Developing an emulator is not a simple task, in fact it should be the most complicated and complex programs to develop. It requires being well documented and having the source code of other similar projects to learn how others have done certain tasks and improve them, but for this before you have to understand what is being done. Simply the previous phase of documentation requires many weeks or months to know the system well to emulator and clear is the system in which it is going to run.
Making a front-end using core from other emulators will simply work just like they do. This is useful for bringing emulators to other systems, but will not improve their performance if you use the same core.
As a reflection I wanted to point out that currently new and future generations of consoles will require a permanent connection to the Internet and the contractual and resource limitations will surely make the emulation systems to be executed through browsers (HTML5 + Javascript), Streaming on the local network or making use of the cloud.
Anyway, this will be my last participation, good luck.