I think I've seen a small 4 wire resistive touchscreen that can be used with the Arduino, but adding in changing PWM signals, possibly rotary encoders and remote control. WITH a touchscreen, dude I like you! haha but seriously, it might be buggy or quite laggy.
It's another option to calibrate it like that, all in all do what suits you best but I think just testing each LDR whilst applying a known current through it would be easiest for me. Time consuming but easy.