The name of this story is bathroom breakthrough! I have 8 sims living in one house. I noticed the area I made for the bathroom had a funky shape, so I thought back to those changing rooms in the sim-gyms where they use an arch to separate showers from the rest of the bathroom. I put in a wall and an arch so this is my way of getting around the 1 sim in a bathroom at a time rule while keeping the bathroom open concept.
When you have 8 sims in a house, there has to be a little bit of sharing. And that is the theme of my bathroom. I put in urinals because male sims can use the bathroom simultaneously. I have had too many incidents where sims try to shoo eachother away from the bathroom and then they both pee their pants. They seem to rather pee their pants than use the bathroom in front of someone.
This does deviate a little from the normal, but it does work. My brother made a crazy house where he put in toilet stalls and put the tub behind a room with huge picture windows.
http://i346.photobucket.com/albums/p408/Anthonydyer/Screenshot-997_zpsoonsdqnw.jpg
http://i346.photobucket.com/albums/p408/Anthonydyer/Screenshot-998_zpsdunjs6l7.jpg