> but the problem there is that they pee in them, and so you have to spend all day changing them, otherwise it becomes very unsanitary
THIS is why I don't do things like belts, sanitary pads etc.etc. simply because for the average owner, they can't change them often enough.
We had entire males and bitches under the same roof, and our girls were upstairs when in season - the only place there was any 'cross-over' at all was the foot of the stairs - I'd let my in season girls out front to do their biz (with me right there!) and everybody else out back. I had to wipe the floor at the foot of the stairs after each 'outing' to lower the angst with the males. But I can honestly say NONE of them ever marked. Needless to say when the girls were in season, it wasn't easy - leaping barriers and making absolutely sure nobody got upstairs! They had their crate up there, open but within our ex-pen. Double barrier. I was home pretty much all the time apart from exercising when the bitches were shut in their crate(s) and the door to the bedroom actually shut. Without proper kennelling, outside, it can be difficult and for that reason, apart from others, my retired bitches were always spayed so they didn't keep having seasons!!!
Just to add the wiping the floor foot of the stairs was only to prevent the boys standing over the drips - it didn't stop them (scent hounds - as if!) knowing full when the status of the bitches........

I'm afraid all this is par for the course, with having entire both genders!