The only time I had to deal with a hybrid progressive/interlaced source I went and doubled the progressive frames so the entire thing was 60fps. There should be a thread started by me where I was asking for help.
Here it is:
https://forum.doom9.org/showthread.php?t=173966
Code:
DeInt=QTGMC(preset="Very Slow")
A=ConditionalFilter(last,DeInt.SelectEven,last,"IsCombedTIVTC","=","true")
B=ConditionalFilter(last,DeInt.SelectOdd,last,"IsCombedTIVTC","=","true")
Interleave(A,B)