all screen size and resolutions are supported automatically with the right settings eg letterbox scaling / full screen scaling / high DPI / linear sampling etc...your decisions rest around window size / resolution / aspect ratio and producing your art assets at a resolution to suit.
I think what you are talking about is letting the user set the window size from within the game.
im assuming it should be possible, maybe with a layer reset.
it would be interesting to know if you can do this.
why don't you give it a try and let us know.....