Very nice, nontrivial original idea! Rated 5 out of 5 stars
I have only one suggestion - as soon as user prefers to use the button - it gets it with a small black triangle near it. Actually the button is a placeholder and the triangle itself makes a job - user gets submenu of 2 items and choose one of them.
If it is so, it'll be more comfortable, if the button itself will activate one of alternatives and triangle - the second without calling the submenu. Instead of checkmark (the second alternative) the color of button can be changed.