IMO during the regular season every kid on the Varsity bench that isn't fufilling an every day role is a liability. Now the every day role could be CR, DP, pinch hitter, pinch runner so I might want 2-3 kids more than the minimum 9. Any kid that sits an entire game without contributing is going to be bitter, no one gets into sports to watch, and if they are good enough to be your next best player, they should be playing JV every game to get better, not watching other girls play.
We play JV simultaneously as Varsity and at the same sites. So any kid you need as a "sub" for Varsity is 100 feet away starting on the JV team if you need them in case of injury or because someone isn't performing that day. Not uncommon to see a kid yanked(even in the middle of an at bat) from a JV game to go over to sub into a Varsity game when needed.
So if you had 16 Junior and senior players, like JBG, you would cut 6 or 7 of them (possibly more, depending on freshman and sophmore talent)?