Essentially what's in the title. With how your house is essentially a useless moneysink outside of the basement I don't see why the punching bag is just cosmetic when it could be providing an actual use by letting me test out damage values and such.
This is also a broad suggestion that I haven't put a lot of thought into, but it may make the house more of an attractive money sink if you could get buffs from it outside of the crafting buffs in the basement. Off the top of my head I'm thinking of the Well Rested buff in Fallout 3/NV. Use your bed, get a minor buff. Hit the weight room, minor buff. Watch some AreaNOW on your pricey flatscreen TV, minor buff. Have a nice home cooked meal instead of eating vendor meat and digging steaks out of the pockets of dead looters.
I'm not asking for any of these to outclass the kind of things you'd get from food, and you could make it so you can only carry one, maybe two home buffs out the door with you until they expire. It would give you a genuine reason to think of investing in your home, because as far as utility goes there is no real reason to buy anything other than the basement floor, the workbenches, and the set of lockers in the laboratory and maybe a couple other storage containers if you want to keep your crafting materials/personal trophies separate.
