The solution I suggested is not to change who trans kids are, but to change the way teams or boys treat them, as in "brown v board of education" we forced everyone to learn to treat all students equally, regardless of their skin color. We didn't tell the kids with darker skins to change their skin colors and try to be white kids. We didn't tell non caucasion kids, "take pills and have surgery to try to fit in with this new group and make yourself look exactly like that new group"
What I'm saying is equivalent to what the league did, which is - "hey, we don't care what your fears or prejudices are, you need to get over them and treat the trans boy (Black man) equally to any boy". They're here to stay regardless of how different they look than you, because they're boys too.
What you are asking to do is put them in a different league completely, because you don't think boys with makeup and bows can compete with boys who wear baseball caps and basketball shorts.