I've seen lots of ideas for M (Multiplayer, Mechanoids, Maritime), but little speculation on the rest.
A few ideas (I don't really feel strongly about all of them, but I tried to think of one idea for each letter):
War - fleshing out the faction diplomacy system to add war/peace mechanics. Trigger ongoing linked raids or appease hostile factions to stop raids altogether. Take/rescue hostages, and manage the opinions of other factions based on who you're at war with.
Order - Add a legal system and set laws and consequences for your colony, overhaul prisoner system
Realms - Add more mechanics to support multiple colonies at once and take control of a section of the world (road construction on the world map, defensive outposts, taxing caravans who pass through your land). Maybe also expands world economy/trading somehow?
Layers - Add multilevel support to colonies for basements and multistory houses (this sounds like too much to manage and has a lame name, but I couldn't think of anything better)
Dragons - Dragons?
External link →