My (current) primary problem with a blanket ban on transwomen in sports is the discrimination and abuse this will bring to ciswomen, the much larger population here. Banning transwomen from sports will affect dozens of people nationwide and isn't my largest concern - a "solution looking for a problem" in some ways. However the more traction this bullshit gets, the more women and girls that perform well or look a little masculine will be ridiculed, have their results questioned, and may be forced to submit to an examination to prove they arent trans. Fuck that noise. Do you want to your successful wife/sister/daughter going through that for sport? And don't be so naive to think this only applies to pro sports or some tiny subset of all sports. This will bleed into amateur and kids sports too, especially if they are proving grounds for later pros. Examples of this already exist.
"XX, XY, Unlimited" is a terrible idea. Even before HRT, people dont fit nicely into those categories. Adding more incentive to steroid use is laughably bad and a great way to kill people. Also, allowing any extreme competition beyond "natural" human ability will call into question the results in the XY category in the same way that transwomen do for ciswomen sports. Every XY competitor that performs really well - many will do better than the worst in Unlimited - will instantly be accused of cheating. Ooooo, maybe we should have this so that men are more likely to experience what women may go through with today's bullshit.