updating on this:

since there was no choice, I went ahead and bought an M fare for half of my itinerary (TLV-JFK-ORD), with a U fare going back. I was actually super surprised DL com offered me a split-class economy ticket (M/U), it's a nice change vs doing all this through the PM line.

so, now I am on the upgrade list for JFK-TLV (I already cleared at purchase for JFK-ORD). what I am trying to get is this:

who comes first? a PM with an M/B/Y fare, or a DM on a lower class fare (anything below M) who is trying to use their GUC? From where I stand, I believe that any one who is flying on a much more expensive economy class ticket, AND using a currency (miles in this case) in order to upgrade, should come before a passenger who bought a ticket for less $, AND is trying to upgrade with a free GUC. Ofcourse, in any case a DM who has the suggested expensive M/B/Y should clear before a PM.

I asked the PM line this specific question, and they had no answer. They also did not know if I in a case where I am not cleared 24hr prior to departure, I can ask to remain on the UG list, or not.

So, I am left with the trusted advice of FT.