That's a joke really? You can't have parts of crew flying around in discretion with bits that aren't, especially if the captain isn't.
Departing from base knowingly going into discretion means that the flight down route is being planned based on discretion. That would not be legal?
Quite apart from that, reflect on this. If one departs base using discretion, once that discretion has been used up, then there is no more to use. So, if, under those circumstances, one departs base and further delays occur down route, then the aircraft could easily find itself grounded at an away station. That of course is one of the reasons why any half decent airline company operates a sensible standby crew roster. But then that is altogether another story.
