Neat idea , but where's the stair horse's ?? Code sez 12" OC with a 2 by tread.
Those treads look to be 5/4" thick and the spacing between the horse's carriages is way to far even if you don't have to meet code , those treads would bow under the weight of a 75 LBS child.
So, neat idea but not a very "good " idea
[highlight] IT could be a killer idea [/highlight], if say some one down stairs opened a draw and some one upstrairs decided to use the stairs , say carring a basket of laundry down the stairs as well!!! Good way to "get rid of" a spouse / unwanted roommate , etc
Sorry to be so negative but ......