Years ago before the introduction of so many constraints, whenever I hired female staff I actually asked their permission if it was okay to discuss any menstrual cycle issues. I prefaced my need to know whether menstruation was a particulalry bad time for them with, "if these times are difficult times for you, in my company you can signal your personal female days to me 'in confidence' and I'll ensure you have only light duties on those days." On particularly 'heavy days' I made my female staff aware that they were welcome to go home or take those days off. I always thought that was in everyone's best interests.
Discussions like this would probably land me in court today, with my motivations being construed as voyeuristic and perverted.
Please keep in mind, I'm not suggesting to anyone to begin mentioning their personal-cycle in job interviews, I'm just saying that I'm aware that hiring managers can often have all sorts of issues and questions when it comes to hiring women that, quite naturally, don't seem to arise as much with men. Children probably being the biggest one.
No offense, but I would be completely freaked out if my manager even mentioned menstrual cycles. To me it's a personal matter. People have all kinds of behind the scenes health stuff going on, and I think if they need to go home early, they can discuss that with a manager on an individual basis. Women's cycles are as varied as women are - some are barely impacted, and there are women that have monthly migraines.
On the one hand, you sound like you are concerned about women, but there is a condescension in it, too, that I can't shake. Like women can't handle certain things, and I assure you they can, and want to be just as "strong" as men. I'm sure a lot of women would take advantage of this policy. I think it also depends on what type of work you are doing. Standing on one's feet for hours in retail with bad cramps would be brutal. With that said, you'd be surprised what advil can do for a person.
My Mom's friends used to have the monthly migraines, and had to get shots to make the pain go away. Someone like that could talk to a manager about it if she needed to, and I'm sure could get a doctor's note or whatever if she needed to miss work.
Ironically, I think this goes back to the original topic - not assuming. You can't assume b/c someone is of childbearing age that they will have kids, or that they will leave the workplace. You also can't assume every woman has menstrual "issues." I think it's a little weird that you are giving it so much weight and thought.