One of the benefits of the ability to do over 8 hours would be to fly any 2 legs. Nothing is firm that it would only be Transcon turns. Say FLL did FLL-JFK-LGB. That would be 8-9 hours and is no where near a transcon turn. But boy would productivity increase. There are many such combo's that could be put together out of JFK. One short and 1 long leg. I don't see IROPs hurting these at all. Remember the 7.5 hour 4 legs east coast parings has a much longer duty day than a transcon turn or a short/long leg combo. 16 hours is 16 hours, whether you are on leg 2 or leg 4 or leg 6 of a duty day.
What I see as long pole in the tent will be to see what rest requirements come along with the expemtion. If the rest requirements are bad (unable to consecutive trips), it is limited or no help to productivity. However, even if the rest requirements are stiff (sts), say 24 hours off after such an event, you could always do one as the last flying event in a 3-4 day commute. Which would still increase everyone's aveage productivity. Just some thoughts...
Just my opinion....
FNG