No I wouldn't because the device is designed to control CO2 using CO2. If you think it can control pH then set it to a reading of 8.5 and see if you can maintain a pH of 8.5.
Well, this is precisely what people maintaining reef aquariums do; they use a supply of kalkwasser to increase pH using a pH controller. The principle is the same, but working "opposite" to us (as we aim to decrease pH).
If you had a pH controller that could control two solenoids, one for CO2, and one for kalkwasser, then the device would still be a pH controller.
My CO2 controller has been set for 20 ppm and it has controlled that level for almost 5 years.
By maintaining a specific drop in PH.
You do realize that a thermometer doesn't measure temperature. It measures volume. So do you call it a volumeter?
Not sure what you are getting at here - I would not say a thermometer measures volume; as temperature increases, the volume of the liquid changes, however, and we use this change in volume to get the temperature.
Are you calling a pH controller a CO2 controller because you think it is controlling CO2? There is no CO2 probe on a pH controller, so then this would technically be incorrect.
As I mentioned, if you have a pH controller that could control a supply of CO2 and kalkwasser, then it would still be called a pH controller, and not a CO2 controller.
Again, for our purposes, a pH controller only controls the pH by increasing its acidity; you are right in saying that it would be impossible for a pH controller (that only controls CO2) to influence the pH to a value of 8.5.