There are group quests availiable right now, although I think they're meant for 3-4 people tops. Still guild-friendly for the most part. Also, regarding diplomacy, you can set up trade routes with other players. I didn't know you could own an NPC town though-haven't seen that yet.
As for starting with a group of players-do you mean several cities in one instance? You choose the area you want your city to be, you know, so you can be as close to friends as you like. Shouldn't be anthing random going on about it, although I'm not sure how the surrounding terrain around your city is created.