Like Episode 4, I see this mostly being a story of Men, with a sideplot in Nan Elmoth.
We do, however, have an opportunity to see Fingon and Fingolfin in the beginning and end of the episode, and we should probably take that opportunity.
Hador does not need to arrive 'at the last minute' to join the Council, but he is travelling from the furthest away, so he's likely not the *first* person to arrive and speak up. I imagine we'll do some set up with Bereg and Amlach at Estolad prior to the arrival of Hador. Which means, we should introduce Hador while he is still in the north.
I think it would make sense for Hador to approach Fingolfin and ask permission for what he intends to do when he goes to Estolad. After all...he has to pretty much know that moving everyone to Dor-lomin is an option, before he puts that option on the table to put it to a vote.
For dramatic reasons, we won't want Hador to lay everything out for Fingolfin, get Fingolfin's permission, and then go to Estolad and lay everything out for the Men there again. So, we do have to consider what is said when on screen. But in 'reality,' I think Hador talks everything over with Fingolfin first. So we should think about what that would look like.
I think it would be awkward to have Hador's first appearance in this episode be him walking into the Council, and then at the end have to sort out, oh, right, maybe better get permission from the elves and run this by them now....oh, hey, we're in luck, Dor-lomin is available!
The 'independent allies' idea should be Hador's...but we should see Fingolfin's buy in as well.