I used encoders in the field, but by the time I was in LA I was wearing too many hats. Choreographer was a full time job.
One way to do real time editing is to use a computer. Maybe a midi control surface for input. A time code on the sound track.
One approach to color mod: Start with 5 comparators and build a ladder circuit to convert a discrete analog color mod signal to ILDA RGB converter. Build a ladder voltage divider with -15V – 13K - 1k – 1k – 1k - 1k – 13k - +15V.
Connect the nodes of the 1k resistors to the – inputs of the comparators so they trigger on -2V, -1V, 0V, 1V, and 2V. This allows the signal in the -2 to -1V range to be defined as red, -1V to 0 as yellow, 0 to 1 as green, 1 to 2 as blue and >2 as black. Put an inverter on each output and connect the output of the inverter to one input of a NOR gate. Connect the other input of the NOR gate to the next higher voltage (non-inverted!) comparator output. This shuts off the red signal when the yellow triggers etc. The black comparator shuts off the Blue when the signal goes above 2 volts. Black is an important part of the color modulation effect. Then take the red, yellow, green, & blue signals from the outputs of the NOR gates to build your RGB output signals.
"There are painters who transform the sun into a yellow spot, but there are others who, with the help of their art and their intelligence, transform a yellow spot into the sun." Pablo Picasso