I'd think if you found a junkyard S series that had the full sensors and wiring harnesses you might be able to make it work? Never tried nor heard anyone try. You are right about the 70 series and older YM systems being not as good as the newer stuff. Biggest issue with those other than the giant moisture missile is the single point calibration the system uses. Need a multi-point to do much good unless you have super consistent fields. 

Would need to change addresses or reprogram things on the computer side