A different Approach: which characters COULD possibly play a part or could we use when developing the storyline? My suggestions:
*Aerandir, Erellont & Falathar - Mariners who later sail with Earendil. We don't even know if they are Elves or men, but because of their names i suppose they are Elves of the Falas. If we need sidekicks for Cirdan we could use them - or maybe Galdor.
*Ainairos - Elf of Alqualonde, spokesman of those who opposed the Noldor because his brother died in the kinslaying. We could use him or give his lines to Olwe's son
*Amdir - Son of Galadhon. Possibly still a child when he lives in Doriath
*Annael - a Chieftain of the North-Sindar at Mithrim, later tuor's foster-father. He seems to have ruled quite independently from Thingol and Cirdan - which is interesting! Did he disagree with Thingol at some point and lead his small tribe away from Doriath? Actually we could decide to built-in such tension - if we wish to.
*Aranwe - father of Voronwe.possibly an old elf and a kinsman of the Noldo royal house.As we have enoufgh Noldo-characters we possibly ignore him.
*Durin - he wasn't cast yet i think! He doesn#t appear in the Beleriand setting, but he was the Automaton-Dwarf in the Aule Episode.
*Ecthelion - later a Noble of Gondolin. We don#t need him yet and i guess we already have enough Noldo-characters.
*Edrahil - a loyalist/friend of Finrod at Nargothrond. He probably might appear in later Seasons, as Finrod (have we decided him to actually appear in the series?) is still a young man, i suggest Edrahil also is still quite young in Season 3 -if we use him at all.
*Elemmakil- Captain of Gondolin. I guess we save him for later Seasons.
*Elmo - Celeborn#s Grandfather and brother of Olwe and Thingol. The character was vetoed quite often so it#s unlikely that he will appear.
*Elulindo/Olwion - Olwe's son? We could use him at Alqualonde or give him Ainairos lines, if we kill off Olwe in the kinslaying.
*Enerdhil - jewel-smith of Gondolin and possible maker of the Elessar. If we use him as Celebrimbor's teacher, this Enerdhil may have been an Elf who has worked with Feanor, a close follower or apptentice maybe.If we like him to appear, i suppose he is still a young man.
*Evranin - a Nando Woman of Ossiriand and later Nurse to Elwing. If we want to use her we could introduce her as a kinswoman of Denethor or Saeros, we might want some more named Nando-characters when the massacre in which Denethor is slain is shown.
*Galadhon - Son of Elmo, father of Celeborn and Galathil. As in the Series Celeborn was made one of the oldest Elves and already was introduced at Cuivienen, Galadhon probably won't appear.
*Galathil - Celeborns brother and father of Nimloth. We might want him to play some role as one of the Nobles at Thingol's court... or we decide to not use him for the series.
*Galdor of the Tree - an Elf Lord of Gondolin.I guess we save him for later Seasons as we don't need him yet. Plus he still might be a child in S03 or not even yet born.
*Gamil Zirak & Telchar - I voted for making these two our main dwarves for the early days of Beleriand, to have some dwarf characters for the audience to identify with. I suppose gamil the young could be around as a lord of nogrod or belegost a 1250-1300,1497 and as an aged dwarf at f.a. 50 at that time he may have a teenage apprentice named telchar. telchar might be around as a young man or ternager at fa 50 and a mature dwarf at fa100 and fa 150. about fa 260 hes ancient.azaghal may be a bit younger, if he was around at 150 he would have been a youngster and very aged in fa 472 when he dies.
*Gimli - an Elf who will later be found as a prisoner at Tol in Gaurhoth. We can decide later if we want to use him or not. We don#t need him yet in S03.
*Glorfindel - a young man/Teen in Fingolfin#s retinue? possibly a son of descendant of one of one of Finwes daughters, Irime or Findis. Maybe Inglor and Aranwe are too?
*Guilin -later an Elf of Nargothrond and father of Gelmir and Gwindor. We might use him as a young follower of Feanors or we choose to ignore this character as he#s not important. If we need some lesser Noldo sidekicks we could use the name.
*Hendor - aged Elf, later a house-carle of idril at Gondolin. We don#t know if he'll play a role in the later series. Again we could use the name if some lesser Noldo characters would be needed.An aged Elf, possibly one of the firstborn could be interesting.
*Ingil Ingwion - Ingwe's son. We haven#t cast him for S02 so he wasn#t introduced. I guess we keep on ignoring him, even if he'll later eventually become the War-Captain of the Host of the Valar in the War of wrath. Maybe he#s still a child or not born yet?
*Inglor - Gildor's dad? as Gildor#s family is dusputed we#d better ignore him I believe.
*Ithilbor - Saeros dad. He could be one of the Nandor Nobles who are with Denethor, if we need some identifyable characters.
*Legolas - a young scout of Gondolin. We may want to save him for later Seasons if we wish to use him at all.
*Mablon - an Elf who will later sacrifice himself to save Turgon and Hurin at the Battle of unnumbered tears. I suggest we ignore this character or use the Name for one of the surviving Nandor if we need one.
*Maeglin - will a young maeglin already appear in S03? possibly not, so i guess we save him for later seasons...
*Meleth - later Earendils Nurse. she might appear in later seasons, i suggest she's still a child or not even born in s03.
*Mîm - the first (?) incarnation of the Dwarf-Lord of Sharbhund i suppose..
*Nargil, Ogbar, Gaurin, Loruin, Saithnar - possibly Noldo-heroes who are named in Beleg's whetting spell.We might ignore them or use the names for lesser support characters if we need some. They could be among the ten companions of Finrod Felagund for example in later Seasons.
*Narthseg - in UT an Elf who helps the Dwarves to betray Doriath. We could ignore him or, what i would like, use the name for one of Eols servants at Nan Elmoth or one of the Followers of Maeglin at Gondolin if we like.
*Nellas - Elf girl and later a friend of Turin. I don#t think we need to introduce her in S03. she's more or less a child so she might not even be born yet. I suppose she is a Nando, descendant of the Guest-Elves.
*Nielthi - Sinda woman of Doriath and Melian#s maid. I think we could use a best-friend for Melian, but eventually Galadriel will take over her part?
*Nimloth - Galathil's daughter and Dior#s wife. I think she#s either a child or not yet born in S03.
*Ornil - Elf of Nargothrond. we might ignore him or save him for later Seasons. I don#t think we need him yet.
*Oropher - father of Thranduil, Noble at Thingol's court. We might use him as a lesser support character or ignore him.
*Penlodh & Pengolodh - Later Elves of Gondolin. they might be teens or children in S03. We don't need to introduce them so early.
*Quennar - a Noldo scholar, teacher of Rumil (?). We might ignore him or use the name for a lesser support character among the Feanorians.
*Rôg - Noble of Gondolin. It is supposed we leave this character out, because his name is unfitting.Might appear as an Extra in later Seasons maybe.
*Salgant - fat Elf of Gondolin. might be a vhild in S03, i guess he save him up for later Seasons.
*Thranduil - a child at Thingol's court. maybe he isn't born yet in S03, we might use him in later Seasons or ignore him.
*Torhir Ifant - possibly an elven Scholar? Not an important character. If we'd need some lesser support characters we could use the name.
*Turgon - did we already cast Fingolfin's sons? I don't remember... I guess he's still a youth in S03.
*Ufedhin - another Elf who helped betray the Sindar to the Dwarves. Like Narthseg we could ignore him or, what i would like, use the name for one of Eols servants at Nan Elmoth or one of the Followers of Maeglin at Gondolin if we like.
*Voronwe - later Tuor's buddy. He might appear in later Seasons, we don't need him yet plus he is possibly not yet born in S03.