[Sombre]

I think messing with Ulmish base stats is not something KO would go for. He likes only a slight difference from other humans - see Firbolg - bigger but only slightly better stats. Same deal with Ulmish - they get an extra 1 hp and that's about it :]

On the other hand, I think their special blacksteel armour could justifiably be 1 or so less encumbering, or even stronger, because it's supposed to be special and because the troops would clearly have trained in it often, building up the muscle needed to carry it around without tiring instantly.

I like Dr Ps idea to give them spells themed on legions of steel and weapons of sharpness (though not necessarily the exact spells he suggests). You could also give them a construction school spell which reduces enc, removes fatigue or gives reinvig, explaining that it reminds the Ulmish of their proud heritage and lightens the weight of the armour. Of course you can't allow the mages to go spamming this on themselves.

I think a standard unit would be fine.

I totally disagree with any suggestion to give Ulm a cheap crossbow unit, because then they'll just build crossbow armies with a handful of the cheapest tower shield guys at the front. Doesn't encourage use of their diverse (and sadly rather crappy) infantry at all.

On the subject of actually hitting stuff - Ulm could justifiably have superior versions of basic weapons. Blacksteel flail, blacksteel sword, Ulmish hammer etc. These could carry att 1 def 1 or whatever, representing the kind of quality seen in the Jomonese weapons.