Hearthfire is good but I think that it might just be on step from great. Why stop at a house? One of the things I loved about Oblivion was all of the dlc for specific character types. Could you not do a combo of those and Hearthfire with the buliding of or what I would prefer the rebuilding of some of the brokendown forts or castles. With quests designed to have you look for certain people for specific upgrades or needing special materials to bulid that needed upgrade that you are wanting. Maybe make it with the ability to add an different space specific for all of the different types. I could see having upgrades that are specific to both the theives that are located via secret door under the castle with a exit to the outside on one of the cardinal directions that would be different depending on if you did the nightingale quests or not, and another also under the castle accessed by a different secret door for those that enjoyed the dark brotherhood with a exit outside located a hundred and eighty degrees from the thieves entrence. Just a suggestion that I hope you will run with. What I also submitted via the contact page.

I think Heartfire is kinda crappy. I like to build a house but why can't you rearrange the wings and rooms you added? MAke a trofy room into a childrensbedroom or make a bedroom in the cellar? or create an attic to store stuff?