You might be right, that in some locations swept wings will help yes.
But in general, at least the seagrass and other types of seaweed we encounter here in Denmark, is mostly in the surface.
And there is nothing you can do about that, in terms of design as I see it...
Even a few pieces of eelgrass on your mast, and NOTHING is fun anymore, you can not glide through carves or 360s without kitepower nomore, and you got a tail of splashing water behind your mast....
Having seaweed on your wing is catastrophal of course, but happens extremely rare in my experience, compared to having something on your mast.
Yes, you can ride on with seaweed on your mast - but is it fun? No way
With the low drag of a hydrofoil, seaweed can be felt a lot more than on other "old" types of boards unfortunately