Slight timeline issue has jumped out at me while looking this over.
Here's our episodes broken down thus far:

Lúthien's imprisonment in Hirilorn is meant to happen as a result of her determination to set out to rescue Beren from Tol Sirion. She has a bad feeling, she consults with Melian, and his plight is revealed. When her intention is made known to Thingol, he locks her up in the treehouse.
If we strictly followed that order of events, we would have to show Finrod lose the duel of songs, and *then* tell the story of Lúthien's imprisonment in Hirilorn, her meeting Celegorm and being under house arrest in Nargothrond, and the assault of Lúthien and Huan on Tol Sirion story...while Beren's story is "imprisoned in the dungeons of Nargothrond". This could be a sort of turnabout is fair play for Beren getting an interesting couple of episodes of introduction with the outlaws in Dorthonion, while we're getting only glimpses of Lúthien's life in Doriath. So, now we'd get three Lúthien-centric episodes while Beren talks philosophy with Finrod and the plot of the 'werewolf that eats the companions' takes on a much more significant role.
...But of course we don't have time for any of that. We have to tell Beren and Lúthien's stories in parallel for Episodes 5-7. So, Lúthien's bad feeling that Beren is going to need her to rescue him will have to start before Beren ever leaves Nargothrond...possibly before he even gets there! I'm not overly concerned with Melian having the abilities of the Mirror of Galadriel. We know she does, and that that is where Galadriel learned it. The moment Beren uses the Ring of Barahir to enter Nargothrond, he has set a course in motion that leads to "Beren needs to be rescued in Tol Sirion," so we can give Lúthien knowledge of that fate before the audience knows what is going to happen. But I am pointing out that we've shifted that timeline, so that when Celegorm and Curufin "invite" Lúthien back to Nargothrond and promise to help her, they do know that Finrod and Beren have set off on the quest of the silmaril...but knowledge of their capture in Tol Sirion (now Tol-in-Gaurhoth) hasn't reached them yet...because it hasn't yet happened! So her premonition is actually news to everyone she tells about it.
Just something to keep in mind while working out the character interactions in those episodes, and considering when and how we reveal the content of Lúthien's foreboding to the audience.
Also, we have three deliberate 'bottle episodes' - episodes that take place within a single setting.
Episode 4 - Doriath. Beren's encounter with Faerie cannot be broken up by cutting away to politics in Nargothrond, etc.
Episode 7 - Tol Sirion. The only other story we might want to interrupt with would be Doriath - but if we want to keep this strictly localized, we can have Thingol's reaction to Celegorm's request at the end of Episode 6.
Episode 10 - Angband.
We also have a couple of other potential accidental bottle episodes:
Episode 9 could take place almost entirely within Brethil and the surrounding lands. We know we want to show Daeron, but he's right next door in Dimbar at this time. Also, depending on where we leave Celegorm and Curufin at the end of Episode 8, we may need to show them returning to East Beleriand in this episode.
Episode 11 takes place within Doriath as well.