The Oath does seem preplanned in the text, so I'm not sure we want to have it spontaneously appear. I think that we need to consider scenes that lead up to the Oath, because we certainly aren't likely to spend 40 minutes in one scene.
The ideas do seem preconsidered, if not preplanned, but I think we could tweak that. I could easily see an actor like Armitage playing it like he's working himself up to a frenzy.
Also think we might need to alter the text,
slightly. Below is my suggestion, with acting cues
"Be he foe... or friend
[glancing ominously over the crowd]
Brood of Morgoth or bright Vala
[same facial expression as when he refused to give up the Silmarils]
Elda or Maia or Aftercomer,
Man yet unborn upon Middle-Earth
Neither love nor law nor league of swords*,
Dread nor danger, not Doom itself
[growing in agitation, clenching and unclenching his fists]
Shall defend him from me or any of my kin**,
Whosoever hides or hoards, in in hand holds
Finding, keeps, or casts from our grasp
A Silmaril.***
Dead we will deal him ere Day's ending,
[almost fae, if not actually pacing than in an attitude of similar agitation]
Woe until world's ending! In witness hear us****
Eru Allfather! To the everlasting
Darkness doom us if in this we fail....*****
On the holy mountain hear in witness [
sarcasm on "holy"]
and our vow remember,
Manwe and Varda!
[scorn audible in their names]
*this change because I think it flows in a more logical progression. Love would stay his hand first, then laws, then swords
**talking in third person about yourself is always weird on screen
***modernization of language to make meaning clearer to audience, removal of "this we all swear", for reasons discussed later
****modernization of language
*****modernization of language
I don't think we can have the sons say it in unison or repeat it back to him line-for-line without it being absurd. But we can have Feanor turn to his family and cry "who will abide this oath with me?" and have each of his sons in turn stand forward and say "I shall." It could be a little hoaky, but I think we could make it work. People tease about the forming of the Fellowship in PJ's film now, but I suspect most people found the scene moving on first viewing.