Since you asked! You could mount your piece of wood on a hinged booklike structure. This is then driven through the planer/molder by a screw. As the assembly moves a roller rides over a linear cam and causes the "book" to open up putting a twist in the board and creating the windward side. There will obviously be an increase in the surface width as the angle increases, which may or may not be desirable. One could then do the curved surface by hand. On the other hand, if one can tolerate a constant width for the blade, it may be possible to have a blade crafted and the curved side done using the molder by simply passing the proto-blade through the machine between two spring loaded rollers. I mentioned molder because you need some maximum space between the planer blades and the rollers (mine has seven inches). You would probably also have to modify the planer/molder, since the height of the board above the blades when going in would get too large. The trailing roller and frame work would be unaffected.
Another possible way to do this would be on a band saw type sawmill. On numerous occasions I've had logs twist due to clamping failure. The blade usually keeps moving during these failures. The trick would be to devise a cam arrangement to turn the piece of wood in a controlled manner as the blade moves through the piece. The wood would be mounted on pivots on the ends, the cam or guide would be mounted along side the piece of wood (or to it's bottom), and as the carriage moves, an assembly mounted to it follows the guide and causes the wood to twist in a controlled manner. Not out of the question.
