I've been thinking a solar-powered catamaran or trimaran would be a nice project. Could generate and burn hydrogen for fresh water. Or batteries for ballast in a monohull. Extra panels can be vertical.. who is going to invent sails with integrated solar cells?.. Oh, I see that exists now. Very exciting!
https://www.hallberg-rassy.com/news/news/solar-panel-sails-2...
And for the unacquainted:
Lin and Larry Pardey, most famously, made a long life together sailing the world, first, in their homemade, engine-less 24ft cutter.
https://en.wikipedia.org/wiki/Lin_and_Larry_Pardey
Cruising in Seraffyn
https://www.amazon.com/dp/1929214049