I just went through the same thing. The first tub I looked at did not have a ledge for a tub mount. I could not find a good long enough spout for the wall faucet, so I ordered a different tub with a deck mount. When I go back to the house tomorrow I will see if this strom plumbing deck mount faucet I used can be wall mounted. It is so pretty. I ordered from vintage tub. Here is a quick pic (bathroom is not yet finished and hand shower is not installed on faucet, but will give you a rough idea)

The only thing I can complain about on the Eaton is it seems that the rubber gasket at the bottom of the tub, which is in the middle of the tub seems to leak? Maybe a plumber install failure? Sometimes when I shift my butt, it pops open too. I get the feeling that the water is going down as I'm bathing in it. It might be an easy fix, but I generally don't stay in the tub too long anyways. I got the bigger of the two sizes they offer. It would easily accommodate two people because of the length if you wanted. I did not get the insulation, but I think it would be easy to do onsite before install if you wanted. i.e. putting some spun type inside the outer cavity. The wall mounted faucet is by Giagni. Builder discouraged me from one of the floor mounted one's. I liked that this faucet filler had the handshower attachment. Have had no problems with it. I really liked this tub because it was one piece vs the Jacuzzi type. I don't think it is flimsy at all. I would buy it again. The idea of a rubber drain hose is just too iffy a prospect for future leaks and this was the only tub with the hard piping at the time. Would not want to deal with the flexible drain cracking in the future.

I'm trying to think of the brand that sells a mounting block similar to what your plumber is talking about. It's not coming to mind - but you would be able to put it behind the tub and never know its there (depending on the angle of the tub) The other option would be having a small wall built behind or at the end of the tub to house the valve - you could also make this a shelf feature for candles or bath products etc.

We got a very good deal on a Victoria and Albert tub, but we had also been looking at "vintage tub" and they had some ones that looked nice. We had bought a Pfister faucet to go with it, but it was too low for our tub when they went to install it. Then we were stuck with having to get a faucet which had the same center distance on the pipes and there weren't a ton with the 7" centers so ordered the victoria and albert faucet but it was almost too high above the tub and so so expensive. In the end we got one I really like from vintage tub and looks wise the polished nickel finish and the porcelain on the handle as well as the feel/weight etc. looks just as good quality for 1/5 the price of the V&A one. Haven't really used it yet as it just went in on Friday so can't speak for long term use.