Dunno about "all aloft", but us sailors on smaller boats have plenty of experience hoisting and stowing the "kite". It's what we call the spinnaker over here.

And yes, this looks like a smashing idea. High winds simply need smaller versions - either that, or they could have some way of rolling the leading-edge in to "reef" it.

As for what happens when it goes in the sea, that's simple - it becomes a sea anchor and you stop. Just need some way of releasing one side, reeling it in from the other side, and re-attaching it.

Graham.