I for one hope the DOT grants it. I have waited 2 hours to take off at JFK in summer thunderstorms. Add on the closed runway and it could easily be 3+. I'd rather just sit it out and get where I am going. Going back to the gate only ensures that it will take even longer to reach the final destination. That being said, if it becomes obvious or even likely that the crew will go illegal before there is an opportunity to depart, the flight should return to the gate.