I kinda get wanting a restricted space for privacy, but unisex bathrooms with multiple stalls exist. The key is making them peek proof and reasonably secure. Once that's out of the way, the difference between a line inside the bathroom and one outside it becomes moot. At that point, it really isn't about having privacy any more since a public restroom is inherently impossible to make fully privacy centric what with sound proofing being cost prohibitive.

If anything, it would be better to have the same space set up unisex (or unigender if you prefer) since it would cost less to make the now bigger bathroom, and improve some of the waiting times for a place to excrete. Well, with the flaw that you would lose the availability of urinals in the real world, so that would end up being a major drawback for space and use management. Point still remains that public restrooms don't have to be segregated to be safe and useful.