So, I've figured something out with Amberstone. Their main weakness in combat is that they can't make footmen or knights. But there's a way to get around that easily against most enemies. The ACE mod gives you the ability to promote a Hearthling to a Lord regardless of which kingdom you're playing as (some retheme the job to something specific to your kingdom, for example Nordlings get a Jarl, while Clan Muramasa gets a Daimyo), which is effectively a retooled knight equivalent. So what you do is you kit this guy out to be an absolute tank, back him with a cleric (or ideally multiple clerics), and then just spam archers for the rest of your units. Just don't try throwing this at Ogo - in fact, I suggest you just delete Ogo and his hoard via the console when they show up unless you've specifically rushed a Carpenter to lv5.