There is a way to link a key to make the window fullscreen, like the "F" key.
I don't know precisely how to do what I am about to propose since I haven't attempted it yet, but I assume that you could make a trigger where, at the start of the layout, a text box appears asking if you would like fullscreen. If the person selects "yes," yes could be made to be the equivalent of pressing "F," and would therefore (theoretically) make the window fullscreen.
I might be way off base here, but it seems plausible to me.