I like your outside shower enclosure. Privacy plus a little protection on a windy day.
I used a different approach for my outside shower. I heat my water in a sun shower bag. It's usually too hot to use directly out of the bag so I mix it 50/50 with cool water in a 2 1/2 gal pail. I then drop a 12 volt bilge pump into the pail and use that to pump the water up into a kitchen sink sprayer that I use for a shower head. I have a step on switch that controls the bilge pump. Usually, 5 gal of water is plenty for 2 quick showers.