this may sound crazy but you would get HUGE bumps from the queer community if you had your sizes in Mens and womens approximate sizes, and had masculine and feminine presenting people model the shirts. gender neutral shopping is having a sizeable push right now, and you functionally double your consumer base at no cost.
Not crazy at all - that's actually a pretty big part of my plan/hopes for the immediate future. If possible, I'd like to go one step further and make clothes specifically for gender neutral / trans* folx. My bf is a trans guy, and I have a bunch of genderfluid/non-binary friends that I've been getting the measurements of/making clothes for to try and figure out what specific alterations work well for different types of bodies. My big goal for the year is to learn a bit more about pattern drafting, and try and release a free shirt pattern for non-binary / masc. presenting folks. (But also, just adding approximate sizes for mens/womens is a really solid idea, and somehow one I hand't thought of yet despite all the above...)
you should talk to the lady who runs Origami Customs - she might have some good info for you. She does a lot of intimates and swimwear for trans and non-binary people on both sides of the spectrum. Who know, she might have some more measurements to add to your alteration charts?