MoveWindow command with relative screen inputs

As I develop packages for others, I would like to have an easier way to position a graph window at a consistent location on the main screen regardless of the system. I am currently relying on the ScreenSizer package.

In the interest of cutting down on package overhead and administration, can I request an update to the MoveWindow command to accept relative screen coordinates? For example, either command below would move the front graph window to the 20%, 20%, 50%, 50% screen location.

I may have asked this same request at some point in the long ago distant past (I recall recognizing a benefit for it as I worked on the ScreenSizer package).