Bottom line what is the reason for this change? Is it to lower the number of fields run during the day? Is it to make the fields more competitive?
If it is to have fewer fields then you need to look at all of them not just masters. You have 4 women who race 35+, you have on average 6 Cat 1-2-3 women and on average 8-12 Cat 4 women. Why not just have an Open Women. You are required to run 8 junior categories that on average have 0-4 riders.
If this is to make the fields more competitive then that is a different reason and you need to look at the makeup of the clubs wanting to change the rules for the masters.
Racing together and scoring separate for points is always a bad idea, and here is why. I go up the road with my team mate who is 60+ and work to take him to the line and he wins another 60+ rider who has no teammates has no one to work for him, is this fair? One category one winner
If you really want to control the number of races run during the day, which I might add is a good thing, look at the whole category system that we have and redo it.
Here is what I would do 12 Categories plus field limits
Pro-1-2 M 100 riders
Cat 3 M 100 riders
Cat 4-5 M 75 Riders (Add additional field if needed)
Master 35+ Cat 1-2-3 100 riders
Master 35+ Cat 4-5 75 riders
Master 55+ Cat 1-2-3-4-5 75 riders
Open Women 100 riders
Cat 4 Women 75 riders
Junior Boys 10-14
Junior Boys 15-18
Junior Girls 10-14
Junior Boys 15-18