The horror, momentarily, abates

It's definitely not going to be that easy.

Let me describe what was there when we moved in.... So, the bathroom has a fairly typical tub, for the purposes of this explanation, we won't go into things that aren't directly relevant.... So for now, it's fairly typical. However, there's no hot/cold controls on the wall, there's a faucet on the corner of the tub basin, with a lever that acts as the diverter, two knobs for hot and cold and there's, what looks like a grab bar, but it actually is a specialty pipe for the existing wand, that actually has a mount for the wand so the shower can be used normally.

Well, without going into too much detail, I'm fairly certain that at least one person cranked on the diverter too hard (no idea why) and basically turned the insides into sand. So now there is a leak that's dripping into the lower levels creating water damage. We shut off the water. Called a plumber.

Thousands of dollars later, our replacement faucet/diverter is odd to say the least: there is no diverter. There's actually two water controls, one for the wand, one for the tub faucet. You control both independently. The wand, no longer has a place to mount, when not in use the flex hose for it retracts into the side of the tub, leaving the head of the wand sticking out of the surface.

For the shower itself, we have zero of the usual trimmings. There's no cutout in the wall for a diverter, there's no threaded pipe coming out of the wall above your head for a shower head. There's almost none of what you would expect.

What I expect, on order to unfuck this situation, is that we'll have to tear out the part of the wall where the diverter and temp controls should be, install a standard diverter box, run a line from there, up the wall to put in a standard fitting for a shower head, then do all of the plumbing to make it all go, which will require copper pipe soldering, something I'm not qualified to do.

Trust me when I say: if it were as easy as you originally thought it was, then this would not be an issue for me, and it would have been completed long ago.

I appreciate that you're trying to be helpful here. Thanks for that, but unfortunately I think this is over both of our heads as amateurs. As far as I'm concerned, half the shower needs to be pulled apart to fix this monstrosity.

Oh. We want another bathroom for completely unrelated reasons. Since we considered this place, we knew that we wanted to renovate to put in a bathroom and some other things. It's always been a part of the plan.

To be brief: the house purchase was a joint venture by myself and my partner with my brother and his partner. We have two family units under the same roof. I won't get into all of the reasons we decided to go this way, but needless to say, there's one shower for essentially two families.

Where the current bathrooms and shower are (we have two bathrooms right now, only one has a shower), they're in my brother's "side" of the house. My "side" of the house isn't even plumbed with water at all.

So the plan is, and always has been, to do renovations at some point to bring water over to that side of the house, and have a bathroom installed for my partner and I. We also want our own kitchen and a couple other small things. There's space to do it, the garage is far larger than we need, so we're going to convert part of it over to be the new bathroom space, and there's a good area in our current "living room" that we want to turn into a type of galley kitchen.... More or Less.

So by getting those renovations done first, we would have a second shower and the situation in the house would just kind of reverse. Instead of us going into their part of the house to get a shower, they would come to our side until their shower is finished.