Gale doesn't really have one, in that sense. The way you deal with him during the game creates his final decision about the Crown. If you tell him on the docks to get the crown after all, while having dissuaded him before, he won't do it. He will offer to sacrifice himself for the group so nobody has to become a Mindflayer, but if you decline and later on decide the final battle is too hard and he should blow himself up after all, you'll have to bully him into it. (No idea how much approval matters) I think, they tried to give him a slow progression instead of one big moment. The thing at the docks is more a wrap-up than anything and he never has a heroic scene like Astarion, Lae'zel or Shadowheart. (Unless you count his dagger animation if he blows up.)
He is also the only one who expresses that he really likes their little group in the "good" version, wants it to stay together and they drive that point home again during the epilogue, so his comment undermines his own character arc. In Astarion's Origin it's something like "we should find shelter" just with more words, which fits much better. But ... not the thread to talk about my favourite wizard. *coughs*
Just saying, Lae'zel, Gale and (I assume) Shadowheart would totally be free to do stuff by the time Astarion's sun-problem hits.
