Thanks for all the hints I see my idea won't work for him. But I have another idea!
Suppose you have a place that isn't big enough to launch only big enough to blow up the kite so that's where you swim out but you can't get your board there because there's a wind shadow.
Why not look up or down the coast a few hundred meters and see if there's a place that is in fact not in a wind shadow? So here's the plan. You go to the place where there's not even enough room to put your kite but you can drop your board there (I would probably throw a carabiner on it and anchor it to something so it doesn't escape).
So the board is in some place where it has wind but you can't swim out. Then you swim out drift launch and then body drag to where your hydrofoil is! If you are hydrofoiling I am sure you are already a master at body dragging so you probably have a lot of options of where to drop off the board.
I'm sure we will be able to figure out something for him eventually. No matter what the location there has to be a way to launch.