On CAV laserdiscs, there is a "white flag" on lines 11 and 274 (or 22 and 23?) that indicate the first field of a new frame. Also, the frame # is put in the first field. MAME has some good decoding code for that.

So if you can get VBI data, it would be possible to automatically construct an avisynth pulldown script.

Unfortunately, the white flag data isn't on CLV disks, since the LD-V8000 was the only player made that could process them. In fact, per blamld the speedup process used didn't tie in with white flag creation - Fox's original plan was to do a 4-sided time-compressed CAV disk!