It really depends on the sport imo. Trans women may retain some more muscle and some parts of the skeleton are largely unaffected, but muscle elasticity, hip rotation, flexibility, and endurance all end up being more dependent on hormones than birth sex in the long term. How much these things matter varies a lot from sport to sport, and the current system is not sufficient to balance these traits even among people of the same sex. Multiple leagues based on broad body types sounds reasonable, but I have no idea how complicated the rules would have to be to make it completely fair, given we already accept a great deal of unfairness currently.