Removing Dale and only giving Dwarves their western settlements + Lunelaith en Nenuial might be a good solution.
Let's see what Gimli thinks about it and I hope Celival is okay with playing another faction
If Adanedhel wants to join, and we remove Dale, we are full.
If he doens't want to join, and noone else shows interest, I might remove Isengard or Dwarves too.