I'm not making fun of it, but I do wonder how a partnership is supposed to work if that's a problem.
I don't exactly watch my husband with pleasure when he pees, but when it just happens like that, it's not a big deal. If you have the space, you can make two bathrooms or at least an extra toilet, but if not, you have to make do with the usual conditions, which is usually just one bathroom in a normal apartment. And that is usually so small that a separate toilet is not reasonably possible. Just like here. I simply think that forcibly squeezing in a toilet cubicle now is a stupid solution.
Then you just have to do it the way it used to be in modest families: the person who is in the bathroom locks the door and for the rest it’s a restricted area during that time. Bad luck for whoever urgently needs to pee then. That means waiting and maybe banging on the bathroom door, so that the person inside hurries up as much as possible. But that's definitely better than doing your business in a dark, small, probably poorly ventilated tiny cubicle.