The green button is a toggle-switch with two positions. One setting is "full screen" (which seems to mean one 8 1/2 by 11 page, no matter how much bigger your monitor might be) and the other is "whatever you had before you hit the green button." Which means if you manually stretch the window to fill the screen you can go back and forth from fullscreen to smaller.

Not quite ideal, but getting a little closer to what you're asking for.