Personally some things I would like:
1. Increased item limits for large houses (400 or more limit inside) (100 limit outside)
2. Ability to use certain furniture inside or out (eg: striking dummy inside, or a bathtub outside for a hot tub.)
3. Ability to have higher fences and a gate with the ability to lock people out of the yard.
4. Different music for each housing area.(Goblet, mist, lavender beds) (Bonus if day/night changes it too)
5. More npcs wandering the wards.
6. Grand company house style glamours.
7. Ability to change the layout on the inside of houses. (perhaps even the ability to place walls/doors/staircases/windows)
8. Better access to rooftop and balcony. (Perhaps even a rooftop terrace to decorate.)
9. Ability to logout in a bed similar to the inn.
10. Ability to change the direction the house faces.
11. In the expansion perhaps an indoor pool to swim in.