I must have missed it.
And seeing as the remote controller seems to control the mixer ( assumed to include thermostatic control of the water flow ) why would you need to control solenoids with a switch. Or is it that you are concerned that a wireless "malfunction" may turn on the shower and these solenoids will prevent waste of water if that "malfunction" should happen. Good idea. except a wireless "malfunction" may affect one of the solenoids while the shower is in use.
IIAC; The solenoids are to control and divert the flow of water between the fixed shower head, hand held shower, and the overflow filler. The regulation of temperature and main on/off function would be done from a of the shelf wireless shower mixer.
joewa would it be possible if you used something like a
Mira Platinum Dual Valve/Controller and then just used a normal mechanical diverter valve to control the flow of water between the fixed shower head and the hand held one. The Mira Platinum Dual Valve/Controller would feed the overflow filler and the diverter valve; the diverter valve would then feed to both the fixed shower and the hand held one as mentioned above. A pumped version of the Mira Platinum Dual Valve/Controller is also available.