I've never seen a working league myself, so I honestly have no idea if they work.
I think an option to disable sexrepro per species is pretty simple to do, so when I find the time, I may try to get that working.
DB3 is still well in progress, and at the moment we are dealing with the issues of collision handling. Progress has slowed down quite a bit due to recent events, so things are taking longer than (I) expected, but it is still under construction, and you will know as soon as we have any big news to share