I think Cygwin is already using Pacman so perhaps you can get it to work without root on Ubuntu and hence on Windows 10.
The next level of integration would be running X11 fullscreen and then launching Windows programs inside that environment. e.g. Word 2016 launched and managed from the Unity launcher.
It seems that there are two main options: - Rootless mode (the default install for VcXsrv), in which your windows are managed by the Win10 WM and integrate quite nicely
- Rooted mode, in which you can use your own window manager, but the windows are restricted to living inside a native Windows window. Using this in fullscreen on a virtual desktop provides a near-linux experience, but some remapping is required so you don't conflict with Windows' alt-tab, etc. Other bits of integration like copy&paste still co-exist nicely.