I would like to see the flitetest guys try to attempt a larger swapable high wing plane see if they cant get a wing span around 50 inches i think that would be pretty cool everything these guys build are amazing!!! then they could call it the ft high wing
Along these lines, I would love to see a swappable bush plane. A nice, high wing, tail dragger with flaps and solid STOL capabilities. It could make a great backyard or park flyer. Experimental Airlines' J-Scott was pretty nice and close to what I'm envisioning.
The oil-based Minwax waterproofing would REALLY have to be tough to depend on a water hull. I'd rather see something more like a Beaver or something with optional pontoons or landing gear or skis. If a pontoon gets waterlogged, it can be replaced easier than an entire fuselage.