Well there's been time for a bit of playtesting and thought... and here are some ammendments to my army list/rules for the Fimir Armies:
Mystic Mist clarification: Units of Fimir will benefit from the cover of Mystic Mist so long as they have one full rank. This means a unit of Shearl, Fimm or Fianna Fimm will be covered if they number 5 or more models, a unit of Mistmor will be covered if it comprises 3 or more models.
Fimm: Fimm now have light armour as standard and may be given shields at 2pts per model.
Mistmor: Mistmor should have 3 wounds, not 5.
Kelpies: Kelpies are now fast cavalry, not monstrous infantry, and have a Move of 8". Rule currently being tested: Kelpies are Incorporeal.
I'll shortly be posting revised rules for Marsh Chariots and human allies. These will feature two new creatures; the Gelfkin and Bansidheiah. Oh, and I will eventually get around to figuring out the Jabberwock breath attack... these guys need some ranged cover!