My ideas on what would make Hearthfire better (sorry if they've been on the forum before, I haven't checked):

1. Torturer's chamber option for cellar
2. More people then just bards, make chefs, etc.
3. Increase amount of children possible.
4. Increase the possible size of the homestead.
5. Make the homestead be near a town, and after making the homestead you can do quests in the town. Once you've done all, or a lot of, the quests be able to govern the town (or hold.) By governing the town I mean be able to choose which side you are on in the war, make financial decision, court decision, everything.
6. Make rebuilding Helgen an option
7. Make some stewards you can enlist conspire against you.
8. Make enemies of your manor, like the battle-borns and gray-manes
9. Make bands of mercenaries hirable for you to kill people, or attempt to kill people.
10. Make children killable.