I think if content with speed of ~20kts or so you can save wing shaping time by simply using a flat or nearly flat bottom surface (main wing). Has been done reportedly many times with good results.
The KF foil as described in the video is for compressible flow, probably the key to it working is that the air that trips into the hollow part expands to whatever volume it "needs" to allowing the wing to act like it is fully foiled. Water can't do this so air will be sucked down onto the wing, making more drag, which does sound inefficient, but maybe results would be ok.
That said, it still would be easy to save a lot of time by only foiling the low pressure side of your wings, if you are not concerned with super high efficiency and top end.
A few stepped hyrofoils have been developed but not ever widely adapted to my knowledge, they look more or less like this (my sketch, from memory....):
- steppedfoil.png (3.56 KiB) Viewed 2036 times
This one was for a foiling dinghy, the goal was to avoid crashing i believe, idea being it might be smoother to have a couple small ventilation areas instead of one huge one, so if the wing surfaced, it would not crash completely at once. Don't think it worked too well, not sure if merely too slow or just didn't work.