How about an app that would run in the systray and each time a window would open it would Auto-Tile, (auto fit) the new window with all of the currently open windows. So with each new opened window all of the other windows are still visible, but smaller of course, and re-tiled so that they all fit the screen.
Probably the snarkiest part would be to decide which method to tile, ...
A idea inspied by the Oberon window manager:
Maintain two columns of windows, spanning the entire width of the screen.
Windows take the width of the column they are in (fixed width windows are centred).
The width of a single column can be manually adjusted from 0-100%, and all displayed windows adjust to suit.
New windows, by default, open at the top of the teft column, taking any extra vertical space equally from any other open windows in the column.
Maximised windows take up the whole column height; minimised windows are reduced to a title bar.
Moving a window moves it to the other column and/or inserts it at a new positionwithin the column using the rules above.