You mount the wing on gimbels on the front of the mast (or maybe the top?), so it always stays level.

I know, you are going to say it will be too waggley just on gimbels. So to stabilize it, you run a staywire down from each wing to the bottom of the mast, but you actually make it a continuous stay that goes around a pulley at the bottom. And then you figure out a way to make it automatically adjust for heel -- so the windward side of the stay shortens and the leeward side lengthens as the boat heels.