We have the option to pay extra to have the house furnished. Why not allow us to re-furnish the home for the difference.
I sometimes like to take the furnishing pieces from one house and move them to the 'main house'. But I'd also like to not have the original house that had the pieces left empty, and really don't want to try and (re)decorate it.
So, why not let us "restore" the home with the original furnishings (these would be copies) for the difference in Crowns.
ie:
If the house costs 2000 crowns unfurnished and 3000 Furnished. Then for 1000 crowns let me 'restore' the original layout; keeping anything I picked up or moved to other homes.
I highly doubt being able to 'restore' a duplicate furnishing would crash the furniture market. But if the fear is warranted, why not just duplicate the items that are found in the Furnished homes but make these versions Bound so the can't be sold. - All that's being changed is the itemID so the dev work should be minimal, and mostly confined to making the system responsible for deploying the furniture when you purchase the home use the Bound versions of the items.
You have to learn the rules of the game. And then you have to play better than anyone else.