Are you looking to make a script or an expression?
I would do it as an expression myself, since each clip would only need 2 expressions (opacity and time remap). It would also be far easier to troubleshoot or adjust as needed than a script IMO.
Make an excel json with the footageName, footageStartTime, footageEndTime, and footageOffsetPoint(last one is optional if you don't want your clips to play from their first frame).
You would need to do 2 parts of the same expression, determine if the layer's source's name is in the json as footageName, and if it is and the current property's name is 'opacity' determine if it has a footageStartTime and footageEndTime and if 'time' is between those values return 100 else 0, OR if it's property name is 'timeRemap' determine if it has a footageStartTime and footageEndTime and if 'time' is between those values to return 'time-footageStartTime+footageOffsetPoint' else footageOffsetPoint.
Finally, just stretch all the layers to the full length of the comp and put the expression on the timeRemap and opacity properties.