Yes, it is huge challenge to make diy foil kite which is comparable to commercial kites. I sometimes estimated I had used 2000 hours for that "hobby" and probably even that is an underestimate. I don't even remember all my kites: failures, too ambitious designs, bad materials etc. etc. It is kind of pity I've lost many original designs because my computers have changed so many times and my file saving practice has been somehow bad
But this is more like emotional lost than any real lost because I have had all major parameters of foil kite design in my head for quite a long time and therefore I can make new designs pretty fast. However I suggest to keep all designs saved and even write down basic or essential parameters of them (unfortunately for example SP does this insufficiently).
I don't see it reasonable to try to compete with race kites, they are now so far developed and so sensitive, difficult and laborious concepts that they are practically out of reach for diy hobbyist. I could design and test that kind of kites too but I'd have to make some prototypes so it would immediately need foreign workforce.
Trying to tailor kite for some specific use (where pure high performance is not all that matters) is much better approach IMO. And it is very possible to reach or even surpass the level of usual mid AR kites like Frenzy, FRS, Pulsion and other simple kites. It should be remembered low AR wave foil kite is the easiest kite type there is.
There is also plenty of room for optimizing designs: what is the best cell count for certain AR, how much AR should be had, what inner structures are needed or is it better use more bridles, how much canopy curve and where, how wide or narrow wingtips, how much camber in airfoil/how thick airfoil, how airfoil is morphed, how cell width is morphed, how much billow in cells, how much coning in canopy, should kite be made of DCF/or perhaps Aluula (IDK where it can be bought), how many levels in the bridle, how inner parts are designed (fabric orientation, weight cuts), how big kite is reasonable (I think 12m for diy worker is reaching the limits, and perhaps smallest size could be 3m) etc. etc.
I'm still a bit surprised Schietwedder has separated bridle design from "kite design", but apparently he has had his reasons and he has also given some explanations of the process. In my design process bridle design is quite central part because cell count and inner structures and also air intake locations are so closely related to bridle, or vice versa. Bridle design shouldn't be any brainer because kite itself is finished and bridle attachment points are there already.
Sharing designs is an interesting idea. But it is two different things to share a kite plans or to share all design knowledge behind it. To share design file or to share patterns of a kite are too different things. Of course quite a lot can be found out from the patterns if someone understands them, but design file shows of course everything.
Many questions like how much AoA kite should have are very specific, some design needs more some less: how much canopy curve, how much AR, how stable airfoil, how many cells are the first things that comes to my mind which have to be answered as well. Discussions of different concepts and solutions are always useful, even though giving precise answers is often too difficult.