First and foremost, not just a house that we can customize and store stuff in, a "skyrim"-like house would be utterly pointless and terrible.
It has to be something along the lines of what was done in Baldur's Gate 2 with Strongholds or Neverwinter nights 2 with the Keep. It must be relevant to the game story, main plot or a side quest, but no random house somewhere on the map, with no interactions, no plot and which would basically be a giant wardrobe. The "house" must add to the story (special banters with npc there, quests etc ...) and add to the gameplay (upgradable house, unlocking special merchant, features, items etc..?).
It would also be great if there were different "houses", depending on your class, on choices you've done etc.