How Could I Explain This to a Plumber?

The faucet for the roman tub is a freestanding antique style, meant to be exposed and reach over the rim of the tub. But we have a slab so getting the plumbing to the faucet is a bit tricky.
I had scheduled a plumber just after my surgery and it was going to be a couple of weeks before he could get to the job. But in a couple of weeks, I realized that I was going to have a heck of a time trying to have everything the plumber needed and be able to tell him what needed to be done. At about $200 a hour, it was going to be an expensive contract. So I was feeling well enough to get started on the project myself at my own slow pace. It is probably costing me way more time but much less money to get the job done.
The plumbing inspector who visited months ago, told me that because the tub faucet has a shower head spray, it needed to have a pressure balance valve to avoid scalding a bather. I already have a whole system hot water tempering valve so I don’t need one at the faucet. I found a nice Newport Brass pressure balance valve on ebay for a reasonable price. It is all brass and quite sturdy. This valve will balance the hot water with the cold so that if the cold pressure goes down, the hot will also go down so as not to deliver water hot enough to scald a person. Although our hot water heater is only set to 140 degrees and is temperature balanced, the inspector told me it is code to have a pressure balance valve at every shower head. The Delta faucets include pressure balance in the rough in valves, but this faucet did not.

The pressure balance valve connections are the two exposed chrome water delivery pipes and the water supply pipes. It needs support but also access as it can wear out and may need to be replaced. So the plan is to create a corner shelf unit between the door and the tub with a false floor for access to the plumbing and a shorter shelf outside the cabinet to cover the valve but expose the chrome piping.
I started laying out boards for the floor plates and then cut some 2 x 2’s because the walls of the cabinet need to be shallower than a 4″ wall. The outside step will be a 2 x 6 that is topped with either plywood or cement board and will be tiled over. So access will have to be through the floor of the cabinet.

The next step was to cut the floor plates and arrange them getting the valve and the faucet enough distance from the tub to expose the piping and allow the faucet to be installed level vertically and horizontally.

I cut the floor plates to include a 2 x 6 at the front edge of the step platform, and the front board here is placed against the 2 x 6 as an alternative. I’m going back to the cut a 2 x 6 for this corner and will move the front cabinet plate shorter to fit.
The position of the faucet will not be centered at the tub end because the pipes have to connect within the enclosed space. But the tub will be about an inch closer to the wall once the back wall is tiled so the offset will be a bit less than it appears in the photos.

I believe this would have been very difficult for the plumber to figure out or even understand if I had had it totally figured out beforehand. This way I can figure it out as I go and end up with a good install with any idiosyncrasies fully explained.
I think this faucet is really beautiful. It came with the tub which was only $100 and I had to buy a matching knob for $98, a set of rubber washers for $10.60, the pressure balance valve for about $45 and two floor flanges that are just galvanized instead of chrome for about $10. Total faucet investment if you agree the tub itself cost $100 was under $175. The faucet of course sells discounted for about $1400 without the risers–sold separately. Kohler still makes them and compared to plastic filled junk, you can tell the difference–not a thousand dollar difference but still a difference.