I would certainly offer to give up my F seat to the GA so s/he could upgrade the next elite on the list, but ONLY if she could guarantee to seat me exactly where I wanted to sit in coach (i.e., next to my companion). I suspect most GA's wouldn't be willing to do this, as it would get way too complicated. How do you get the non-elite sitting next to my companion to take some other random seat? Well, it's easy if you offer him an F seat. Maybe if the #1 on the upgrade list is in a good exit row seat it wouldn't be too difficult, but you have to find a GA willing to go the extra steps. Otherwise, I think swapping on your own is fine when there isn't any other reasonable alternative.