I built a teardrop trailer ( https://www.instructables.com/id/Teardrop-Trailer/... not mine but to give the idea) in 2011, this year my wife and I camped in it for a couple nights for our anniversary. While the trailer was great and allowed us to sleep peacefully and dry through 1" of rain dropped by a thunderstorm (try that in a tent) I still had to bring our changing tent as we didn't have a place to stand up for changing. Thanks to camping mid week we didn't have any real close neighbors at the campground, so the short step from the trailer door to the changing tent was no big deal, but if the spaces around us had been full, getting to the changing tent would have been a pain.
I had this idea in my mind but didn't have time to construct it before our trip, from now on we will both have a changing room outside our doors. if the weather is rainy I figure a golf umbrella over the ring would keep us dry.
4/15 Since this I'ble was written we have gone on many trips, the side tents are great! they almost double the private space of the tear, allow us to sit in the open door and get changed, just like the bed at home. We also use them as a potty tent, and have showered inside them as well.