I don't why but I think you are under the impression that I am trying to make you change your mind as if I own a huge chunk of the mining industry, it is actually the exact opposite, I am a buyer I would most certainly love to see the likes of your idea get implemented so I can buy cheaper gears.

But I know for a fact that it won't make any economical sense, ignore the little details and just look at the big picture, you are trying to compete with multi-billion dollar companies, if Bitmain, MicroBT, Canaan or Inno had a way of making an S19 equivalent for less than the market price they would have done just that, they won't leave this money making opportunity to the average joe.

This means there are some hidden and unknown costs that you don't seem to be aware of (I am not aware of them either), you seem to be simplifying the matter way too much, this is either overconfidence or pure misunderstanding of how things are.
 
You claim that you can make a mining gear that goes for 14k for just under 6k + the PCB cost, then my words hold no meaning at all, go ahead and do it, meanwhile, you might want to test on a cheaper gear like the S17 or S9 given that the success rate of this operation isn't too high.

Good luck