The problem with this is there are times when there are multiple races in the same field, and no way to distinguish who is who. I lost a race to TKP's coach back in the day because I was racing against him and the 35+ guys, while another guy in the break was seemingly dying. Only he knew he and I were in the 45+ race and I was only concerned with winning the race. I got attacked and countered and down the stretch I lost the battle. And then this guy outsprinted me for the 45+ win.
The NYS and NJS state RR were actually the same race, and then had 40+ and 50+ combined. So they were pulling four separate races from one field. Gets confusing in hurry from a tactical perspective.
In NYC it's been standard issue to combine masters and women, but it never works very well. I hate to sound sexist, but so it goes, they mostly get in the way, and in the case were pretty sketchy. One women ended my buddies career causing a crash that shattered his elbow. It, of course, could happen in any number of ways (I have two surgeries caused by men, and one by my own ineptitude!) but in his case it happened that way and left a psychological mark. Issue is the courses aren't selective so they can sit in and then just tend to get in the way. Rotate up but not pull through...stuff like that.