How do you use shower controls?

If you are planning a bathroom remodel with a designer or a contractor, you have likely been asked what kind of shower system you want. There are only two basic systems, and chances are you have used both at some point, but the technical plumbing lingo can make it all a bit confusing.

Pressure balance shower system
With a pressure balance valve, you have one lever that is your on/off function and controls only the temperature of the water, not the volume of the water. When the valve is on, it is all the way on (2.0 gallons per minute in California). You cannot decrease the volume of water coming out, but you can always use an adjustable shower head to change the pressure.

Thermostatic shower system
With a thermostatic system, you typically have two levers or controls. One lever controls the temperature of the water (thermostatic valve), and a second lever controls the volume of the water and the on/off function (volume control valve). This system allows you to set the temperature once and for all so that each time you take a shower it’s set the way you want it. You can also adjust the volume of the water coming out, but 2.0 gallons per minute is still the maximum. This valve is more complex and therefore is more expensive than the pressure balance valve.
Shower systems by Douglah Designs featuring Rohl (left) & by Kallista (middle & right):

A pressure balance system

A thermostatic system with volume control

A thermostatic system with volume control

Diverter valve
With either system, you can add a diverter function to the shower. A diverter allows you to have more than one shower head (or a tub/shower combo). In California, you can only have one shower head running at a time, so each shower head needs to be on it’s own diverter port that cannot be operated at the same time as another, and the valve cannot have any shared ports. Today, “all-in-one” valves are available that combine the diverter, volume control, and thermostatic valve on one escutcheon plate for more simple look.

So what’s popular?
Our design team usually suggests a pressure balance system in hall, kids, and guest bathrooms, and a thermostatic system with a fixed shower head and a handheld shower head on a diverter function in the master bathroom.
Shower systems by Kallista & valves by California Faucets:

A thermostatic system with volume control and diverter

A thermostatic system with volume control and diverter

A mostly obsolete system in California (though with the right diverter, would still be allowed)

Pressure balance valve

Thermostatic valve with integrated volume control

Thermostatic valve with volume control and diverter

I'm doing a remodel and I wanted to ask for your advice.

I have a fairly large shower spanning the entire width of the bathroom (see the plan below). I'd like to set up the showerhead at one end of the shower (the furthest point from the 5'6" unmovable glass door) - but I worry that with that plan, I won't be able to turn the shower on without getting wet before the water warms up.

What I would like to do ideally is to have the showerhead where it is on the plan, have the mixer right there, but add a secondary set of flow controls where the red arrow is on the plan. Is that possible? Is it crazy? What kind of equipment would I need to add to make that happen?

Thanks in advance!