One thing you might like to consider is what I did: no wall-mount shower head at all and only the hand-held shower head on a bar. This would be a way to save money, too. I had this at my old house in both the master bath and the kids' bath, and I did it again in my new house when we renovated. I really like having the hand-held for washing the walls, not just for the weekly scrub, but for rinsing after every use to get the soap off and prevent scum from forming. I also like it for washing intimate areas and the kids' hair, and it's nice to have the shower head height adjustable on a bar if any children will ever use your shower. I have never missed having a regular wall-mount shower head. I have used Grohe and Hansgrohe shower heads. One warning about the rain shower head is that some people have complained that they have insufficient force to rinse out thick hair. I have never used one, but you might look on the forum.

What you want are readily available from most manufacturers. As an example, the wall mount Kohler valve is K-687-K or the deck mount is K-8549, trim sold separately. Here is a link that might be useful: Diverter valve

Although, we are re-doing a bathtub/shower, and I am replacing it with showerhead, handshower and tub spout, and had to get all the pieces separately (didn't care for the Symmons styles). We are going to use a delta pressure balanced valve (but it has separate handles on one valve, one for water volume and one for temperature), and then a diverter (to go to either tub, shower, or handheld). The rest of the parts are going to be Grohe, but they are all from different style lines (yeah, it sounds like Frankenstein but I don't think it will look that bad).

My contract with my GC provides that I supply the fixtures and obviously the rough stuff as well since it has to work with the fixtures. However, at some point someone who understands technical plumbing issues should be doing the purchasing or telling you exactly what to purchase. When I was selecting my shower fixtures, my designer obviously helped me with the look of the fixtures but she also explained the difference in shower valve temperature regulations - thermostatic versus pressure balance and then I decided which kind I wanted. The shower fixtures you select would then determine what rough you needed and she was responsible for ordering those. In other words I selected the style and how I wanted the end use experience to be like but she was responsible for making sure that everything necessary was provided to the GC so his plumbers could install what I wanted. So although I was providing the fixtures to the GC, someone with technical expertise was guiding me in the purchase.