I would have pictured the starting archer line units to be slingers rather than wielding crossbows.
I also kind of picture a more culture orientated civ....with that culture very much centreing around yeast and hops! Perhaps they could get additional culture/happiness boosts for Taverns/Inns?
Are you considering an affinity at all? Presumably - considering the thief element - you'd be thinking Shadow? I'd guess the tempatation would be to then say Nature - but nature is a bit well worn, and the Svart already have it in combination with Shadow. Perhaps then Air - representing a playful element to their nature?
For the final palace resource - what about Ale?
If you go down the ale side of things, perhaps then - after looking at the Bestiary Kael put together - you could 'ally' them to Clurichaun? This wouldn't be represented by units as such, but perhaps the Clurichauns would play tricks on invading enemies so that each enemy troop in Jernoran territory has a risk of perhaps losing weapon bonuses, or taking very minor damage, siege engines losing movement for a turn, or horses bolting (unit moves off randomly)?