Tom,
I like your suggestion. I've been wondering about PAM too. The target is to make the nylon line more slick. Water as a simple solution didn't work. To lubricate the first few feet that contact the crotch would speed the descent of the falling weight.
An oil compatible with maintaining nylon strength would be a winner.
The guiding principle is that tree entry is the front door to recreational climbing. It needs to be a welcoming activity, not a barrier. There are pitfalls that can eliminated and or reduced. This benefits the newcomer to recreational tree climbing.
Regards,
JimK
Keep FIT - Fun In Trees