CP:
I still think mercenary camps that spawn soldiers or equipment would be awesome. I'm thinking these should be on the borders of the plains biome, as that makes more sense than somewhere in the middle unless it becomes a balance issue.
A swamp witch that gives you potions/poisons is a must.
Likewise a wizard for magical tool drops or lapis lazuli/emerald bits could be thematic and not too overpowered.
Elven outposts that give baby trees, lumber, arrows, and string.
Horselord, a wandering man with a donkey that will trade gold for leather.
One dwarven surface merchant colony that handles the enchantment/anvil service, that way players dont have to invest a great deal of iron to make anvils ALL the time.
Content:
I still love the idea of a static questline that would be optional and a little pve or whatever. Maybe a dungeon delving where player-kings could temporarily lay down the sword and adventure together for split loot. Personally I feel that desert region is just begging for an adventure-pyramid related trapfest.
Also it times of global peace maybe travelling tourneys and pit fights for glory could be held at the royal courts of the realm. Just a thought.
Finally there should be a relic hunt out there with like a kind of treasure map in pieces and riddles and clues hidden around the plains biome in every sovereign land (for fairness) and it all leads to something earthshattering, but not easy to find (maybe held in Squirtler's hands or something so that it couldn't be stumbled upon).