Gale is definitely high on the list of sacrificial lambs should they be needed just because of how he betrayed Mystra. But his story is somewhat compelling as he used to be an extremely powerful archmage and there are probably interesting things that can be done with the Netherese Destruction Orb after we extract it from him. His story might lead to powerful items and artifacts and if need be you can probably off him during or after the end of his quest.
