For our FWC outside shower, which is on the driver's side (Hawk), I cannibalized some parts from an old tent. The tent had the standard fiberglass/shock cord poles, and at the bottom of the tent where the poles go, there was the older style of aluminum "studs" (like a heavy piece of aluminum wire that is bent into a lollipop shape) which attach to the tent with key rings. The metal sockets at the end of the tent poles fit over the studs when the tent is set up.
I took two of the aluminum studs and bolted them to some small aluminum angle brackets I had. The brackets get bolted to the jack brackets on the driver's side corners of the camper. Basically, you end up with the tent studs mounted like tank turrets to the jack brackets. I cut down one of the tent poles to fit between these two studs with enough extra length to make a shallow semi-circle that runs the length of the side of the camper (horizontal to the ground), to be used as a curtain rod.
I left the tank turrets loose when I first put the pole on them, so that the pole lets them find the right angle. Then I tightened the turrets on their brackets so that the angle is preserved. Now the turret/angle bracket assembly can be bolted and unbolted to the jack brackets when needed. I used all nylock nuts on these so that when we are on the road, they just stay on the jack brackets. We found an oddly sized shower curtain on amazon that fits the length and height of the tent pole curtain rod, and used cheap plastic curtain rings to reduce weight. When we hung the curtain the first time, the curtain rod sagged a lot under the weight, so I rigged up a length of paracord with hooks on either end. One hook mounts to the FWC roof bracket on the side of the camper (near the front), the cord runs down through an extra ring at the center of the curtain rod, and then up to the FWC roof bracket on the rear of the camper. This supports the curtain rod perfectly, and the height can be adjusted slightly by sliding the ring that the cord runs through slightly off center on the curtain rod. Next I put grommets along the bottom of the curtain. On asphalt, we tie rocks to the grommets with cord, on soft ground we stake the curtain down. Both methods get rid of slack in the curtain for breezy times. I got four neodymium magnets that are coated in plasti-dip type stuff. We use two of these at each end of the curtain to stick it to the truck body, which allows us to get the curtain ends to fit right against the irregular profile of the side of the truck. The coating on the magnets is important if you like the paint on your truck, but always wipe the grit off of them before you stick them.
We have one of those small folding wooden shower platforms (one of the few items we bought at Camping World during our only visit to that nightmare). Our first run, we just stood on that while showering. It worked but it was a bit of a gymnastics act. I came up with the idea of using a decent quality tupperware tub to stand in while showering. Initially I planned on having a length of drain hose hooked to a bulkhead fitting in the side of the tub, so that shower water would drain out as we showered. That plan did not work and I decided to plug the fitting and forget about the drain. It's actually better to be standing in shower water as weird as that sounds. I like it because it is precarious to reach down and wash my feet in this setup. Under the unspoken backcountry hygiene code, it is acceptable to rely on standing in soapy shower water to wash your feet. My wife likes it because it makes leg shaving easier. It also helps with water budgeting because you can see how much water you have used as you shower.
This setup works for us. It's a little "exciting" at times when we are in a campground as the shower side of the camper is usually facing the street, but we haven't been cited for indecent exposure yet. The tube we stand in is storage for the whole kit. The wooden platform fits in there, along with the curtain, rod, stakes, and even our towels. When I take down the curtain, I unhook the support cord at both ends, leaving it hanging from the middle curtain ring it runs through. Then I slide the curtain so that all of it is hanging from the center tent pole section. I unhook one end of the pole and fold the pole "around" the curtain rings (shower curtain still on). Then I unhook the other end and fold that half of the tent pole around the curtain as well. Then I roll up the curtain around the whole thing, so that it is all ready to set up quickly the next time. It does not take me more than a few minutes to set up or break down the shower kit, and it all fits in the tub, which travels under the side-dinette table in the camper.
When we first got the camper 12k miles ago, I thought it would be nice to have the option of the indoor shower. Now I know we would never use it. I think if we had a flat bed model, it might be more usable, maybe. We love the FWC, but it is just not big enough to mess around with a shower in there. We do not have any kind of toilet; for both of us the idea of having a toilet basically inside the kitchen/bedroom/dining room is not something we are remotely interested in.