The problem with the LDR is that it's response is very slow. For a low pass filter this is exactly what you want although you have no control over the time constant as you would if you did it "properly". As I said the problem is the none linearity of the system, so yes it would work but it would be a bit like trying to control something with a log pot instead of a liner one.
The thing about when I was young is that you could invent something but not get the information out to tell everybody or in fact anybody. I also independently invented the watch dog timer for microprocessors in 1974 but I didn't call it that and never published the design. That's why I am still an engineer and not rich, still it keeps me occupied.
