Citizens and Guards
 

I think its not hard to notice why kingdom islands are a bit boring... you run over the island... see 2 or 3 towns... maybe a player.. but no one else!
How about adding some simple NPCs to those towns? some of them could do something, some could say a word or two, some might buy stuff from you and others are just there to make those islands look more lifely...
Also, at town, castles and strategical important places there should be guards... NPCs carrying weapons and armor wich attack members of enemy kingdoms (lets say the guards should be as strong as a lord) and even if there is no war, it would be nice to see some guards, also inside castle... most castles are even worse than the islands! there is NOTHING! Forest castle has some small rooms and samurai castle looks quiet good now with the furniture but still, no one there!
Im sure it would not be hard to implement this since its only some easy NPCs wich would make the whole game far more intresting...

Sounds like a good idea - simple guards walking here and there shouldn't be the problem. If it works on Zorbi castle on classic, it will work here, too ;)

Stuff like this was originally intended to be built for kingdoms, but it's probably not going to be added for a million years.