Found a family tree and removed some people. They are not shown, but still "exist":
I circled those that can be main characters this season. The rest could be supporting characters. The lighter areas at the bottom are people I suggest that we wait to introduce. F.eks. Baragund and Belegund aren't very important, except for being part of Barahir's band, so next season is their thing.
The rest of the Haladin could be introduced during the time Húrin and Húor stay with them in Brethil (ca 457, same year as Tol Sirion is taken by Sauron!).
In an earlier post I suggested that after Bëor dies there is some kind of unrest among men in Dorthonion because of the differences between the immortal elves and mortal men. I now thought that what if that is shown through some kind of conflict between Boromir and his cousin Bereg? Boromir supporting the elves, and Bereg against them. Then we show Adanel and her cousin Amlach arguing. Finally there is a big council when Amlach speaks very harsh things even lying about the elves. This leads Bereg to go east with a lot of men. It is revealed that it wasn't really Amlach speaking, and he goes to serve Maedhros as a way to maybe compensate for the losses.
Later Boromir witnesses the failed love between Andreth (his daughter) and Aegnor. There is some of fighting in Aglon and Hador, who has been visiting old Amlach, receives Dor-lómin from Fingolfin as a reward. Boromir asks Angrod/Aegnor if they will give his people their own lands too recognising that it's better for his people to live more separated from the elves. No more failed love, no more longing for immortality. He receives Ladros.
We have Haleth's story before the Aglon fighting. And Andreth through all of the Boromir, Aglon and the rest of the season. Spreading out the Athrabeth. Bregor (her brother) can be a supporting character too. He is later renowned for his bow, which became an heirloom of the House of Bëor.
We could also do something with Barahir before he saves Finrod. Bregolas (his brother) could be a supporting character, he dies in the Bragollach. Bregolas is also the father of Baragund and Belegund who are members of Barahir's band of outlaws. Beren and Emeldir (Barahir's son and wife) could also be characters here. Emeldir will lead the refugees away to Brethil during the Bragollach.