I think if you believe an arbitrator is going to benefit the FedEx pilot group by raising a pay rate, you need to review the last 777 arbitration results.
Outside entities are not going to pull up your rates to industry leading benchmarks, or at least they haven't in the past. I thought they would last round, and I got schooled. "I think the mediator will see things our way..." is hope. I had the hope wrung out of me a few arbitrations back.
Judging by the numbers who eagerly bid the jet to be part of the initial cadre, it appears the 777 rate was not only adequate, it was desirable.