In r/fo4 I asked for commenters to suggest DLC. Here, you can vote on your favorite ideas!
DLC Main Theme:
1) Skyscrapers Only (Verticality, Sky Bridges, Ground Most Dangerous and irradiated)?
2) Turf Wars ("Hearthfire" for settlements). No specific story, just more/better settlement tools. Ability to align with sub-factions (raiders, mercs, ideologies). Settlements can be conquered through fighting, subterfuge, or propaganda. Compete for control of settlements.
3) HP Lovecraft. Uncover ancient underground places throughout the commonwealth with a final area/city expansion "deep under the earth" you can visit.
4) Visit Moon, which had fighting and bases before the war.
5) "Vault-Tec Island" - Basically a supervault the size of a new land. On East Coast.(Martha's Vineyard?)
6) Take Yangtze to China (DLC location - editors note, mobile hub submarine base would be cool).
7) BoS Outcasts and return to capital wasteland
"Miscellaneous" Ideas:
1) Three Dog Radio guy updates specifically on what the player's doing.
2) GIDDYUP-BUTTERCUP power armor
3) "Peace" option
4) DLC features a new city size settlement in pre-existing Commonwealth location (maybe new faction hub?)
5) Underwater locations
Your vote: Settlements with turf wars