Faelivrin, after you left last night, Nick and I discussed whether it should be Fingolfin or Glorfindel holding Turgon back in that scene. Fingon was also brought up as a possibility.
Glorfindel *is* awesome, and he *is* there on the Helcaraxë, presumably with Turgon. So, he was an option.
We chose not to use him for a few reasons. One, he has not yet been introduced. So, he would be quite clearly "random blond extra" in this scene, not Glorfindel the Awesome. Glorfindel can be snuck into the background of a few scenes, but he does deserve an intro - a scene where his character is introduced to the audience. So, as far as I'm concerned, we have not yet done that for him in this project. Until we do, he's a nameless blond elf.
For another reason, what was required in this role was someone who would be telling Turgon what to do. Fingolfin is his father and lord; it makes perfect sense for him to order Turgon to stop. Glorfindel and Ecthelion are Turgon's underlings. Physically restraining their lord is something they could do (especially to save his life), but surely that would require a bit of explanation or background? Of how they are so close to Turgon and love their lord, etc. Otherwise...what we are trying to say in this scene gets muddied. If we don't know who these people are or why they're attempting to save Turgon, it's not really clear what we should think about them; they're just there. The relationship between Fingolfin and Turgon is well-established and clear, in contrast.
But the most compelling reason was that Elenwë's death is a direct result of the decision to cross the Grinding Ice. We are literally showing the ice bucking up and tipping her into the freezing sea. Whose decision was it to cross the Ice? Fingolfin. And so, showing his reaction to his daughter-in-law's death is also important. Eventually hearing Turgon blame Fëanor and *not* his own father for this tragedy will make more sense if we see Fingolfin here, saving Turgon from sharing Elenwë's fate and mourning her loss with his son.
Glorfindel is still there. Time passes in this scene. So, we have the initial accident, where Turgon is alone with Elenwë and Idril; the grinding ice has separated them from their traveling companions, so that Turgon is standing alone when he makes the desperate bid to save his daughter. Once he rescues Idril, his immediate companions have reached the site of the accident - he can pass Idril off to them and dive back in to save Elenwë, despite their cries of protest. Someone will need to be there to wrap a blanket around Idril in this scene. It might be Aredhel; it might be Glorfindel. I don't know. But then when he comes up empty-handed, clearly suffering from hypothermia, now everyone is standing around silently, knowing that hope is lost - there is no sign of Elenwë. So when he turns back to the water, to jump in again...that's when Fingolfin (who arrived sometime during all of this commotion) steps in and intervenes.
I agree with Nick that the most obvious place to introduce Glorfindel and Ecthelion will be in Nevrast, when Turgon has established his court. But if Glorfindel were to wrap a blanket around Idril in this scene and look on her with pity, that wouldn't be a bad thing.