If safety is a potential issue, you could also make the benchwork in front of the window removable, like you might do for an entry doorway. A bridge? Or make the benchwork narrow enough that it would be easy to climb over. Maybe putting a step-stool nearby to give you a boost to get through the window. I know this is kind of "stream of consciousness", but the type of window would make a difference, too -- crank style vs. sliding, double-hung, etc. I wonder how many people even think of this issue when they block a window?