Or perhaps it's better if Nerdanel finds him together with the sons and it is implied that Fëanor and his sons have been somewhere without Nerdanel (rehearsing the Oath) and she asks where they've been, but they don't give her a clear answer. We get the feeling that, even if some or most of the sons have nothing against their mother but in fact love her very much, they have sided with their father. Then we can have a short buildup of the tension seeing the Noldor waiting in the square, catching the arcs of Finarfin/Galadriel and Fingolfin/Irimë.
I don't think I want to do this, because I want us to leave open the tension and drama between the sons for most of the season. I know it's a significant change, but I don' t think I want the sons swearing under the torchlight in Tirion -- one, I want the Oath to be more impulsive than that, and two, I think we'd be losing a lot of potential pathos (especially for Maedros) if we have the sons in lockstep from day one. I also think that we want to do a slow-burn for the dread and doom of the Curse.
If we give the Oath just to Feanor at first, then we can unfold the full meaning of it slowly throughout the season, and the moment when he begs/orders his sons to renew it before his death could make our audience sick to their stomachs, because we
know what these "young men" are about to commit themselves to. The Oath will have punch with Feanor because we've spent so much time with him: I think we need to spend more time with the sons before we give it to them, too, unless the full import of their swearing will get lost in the shuffle.
So what did Corey mean by giving Nerdanel Galadriel's role?
In the third version of Galadriel, recounted in Unfinished Tales, Tolkien envisioned Galadriel as an antagonist to Feanor, arguing against him at Tirion and going to Middle Earth mostly to keep an eye on him and stop him from doing too much damage. While I think it's important that Nerdanel stays in Valinor, Corey has suggested earlier that she be his interlocutor in Tirion. I know some have suggested that she not speak up in public, but only in private, which could work (her storming up to him afterwards hissing "have you gone
mad?" for example), but unless we want the scene in Tirion just to be Feanor's speech, with no other voices raised, I think her voice would have to be included in the debate. She's not going to sit quietly and let her husband and his brothers settle things alone, I don't think. And this isn't her challenging him on how he conducts his family affairs, which is a private matter, this is a matter of great import for their whole people; I don't think that, if there's a debate, she'd feel as if she could afford to wait to speak privately with her husband.
I do think, however, that she shouldn't say "I would never go" or something like that. I want her husband and sons to know she's opposed to the idea, but be able to believe that she'll go along with the majority opinion once she realizes she lost the argument -- and therefore be shocked and hurt when she "chooses" the Valar/Valinor over them.