First of all, sorry if this was posted before. I was reading back some previous discussions, but I haven't seen any suggestion about this.
As you can see from the title, my suggestion is to move the houseguests to a different category. This function was a great addition for the housing system, but having them as special collectibles limits the use of them on bigger places. I admit this idea is a result of a long decorating session, and while pets, mounts and assistants counts toward the special collectibles as well, this make many of the houseguests gathering dust in the inventory.
This of course is just my opinion, but I'm curious if I'm alone on this subject or not.