Oh, it was probably meant to be Nargothrond, and didn't get moved to the right episode. Oops. Let me update that..... [the tower of Minas Tirith at Tol Sirion is already built in Episode 4]
Finrod should be in Doriath (for some unspecified reason - visiting Galadriel?) when Círdan arrives with the message that the Fëanoreans burnt the ships and the Noldor are guilty of crimes against the Teleri.
But if we give Finrod some official business with Thingol at this time, that could make the way the kinslaying reveal plays out more interesting. So, what could they be discussing? Finrod could be promising to keep safe the pass with his tower at Tol Sirion. This would be meant as a reassurance for the elves living, say, in the Forest of Brethil, which is outside the Girdle of Melian. Perhaps Beleg and Mablung are in favor of 'patrolling' well outside Doriath's borders to ensure the safety of the Sindar....
In the book, the sons of Finarfin are just visiting Doriath to visit Galadriel and this coincidentally happens to be the time Cirdan's messengers bring news of the kinslaying to Thingol. However, if we plan to have Cirdan himself deliver the news, it might be interesting for his visit to be anticipated and related to Finrod and Angrod's visit. Perhaps all three could be visiting Thingol as part of a war conference to coordinate Noldor/Sindar/Falathrim efforts against Morgoth.
Finrod and Angrod could arrive early and visit Galadriel before the conference. They could tell Thingol and the others at the conference (maybe Beleg, Mablung, Celeborn, Galadriel, and Melian) about the progress the Noldor have made with their fortifications in the North, focusing on how the Noldor are protecting the Elves in Doriath and southern Beleriand. Then, they could request that Thingol's people return the favor, and Beleg and Mablung could express their support of this. Maybe Finrod or Angrod could read from letters from Fingolfin and Maedhros requesting aid from the Sindar in the form of supplies and/or troops.
Sometime in the middle of this, Cirdan could arrive, go immediately to Thingol, and tell him that he needs to speak to him in private. Thingol and Cirdan could step into another room, where Cirdan would tell him about the kinslaying. Then, Thingol could storm back into the conference room and confront the Noldor.
After Thingol issues the ban on Quenya and calms down, the war conference could pick up where it left off, but Thingol would be much less willing than he previously appeared to support the Noldor. His response to the requests for aid could then be a way to show his relationship with the different houses. For example, maybe he could agree to send supplies and troops to Finarfin's sons, just supplies to Fingolfin, and nothing to the Feanorians.
