Just use a digital display to tell all drivers how long it is to the next light change. If you do that, there is no substantive reason why the cameras are objectionable. If you don’t do that, there is no reason to suppose that you are putting cameras in for any other reason than revenue.
Decades ago I saw an invention outlined in what, I think, was Popular Science. The stoplight had a rotating arm and the position of the arm designated where the stoplight was in its cycle.
The "countdown clocks" that I've seen should be a requirement before any red-light camera gets installed.