That shelf system has made a great catwalk. Newton and Newt should get a lot of enjoyment out of it. I like the location of the new cat condo in front of the window. That spruce tree outside the window should be a great haven for birds, and be great entertainment for the cats doing birdwatching. I don't think the shelf system will have any effect on the value of the house on re-sale. All that would be needed would be to fill the screw nail holes and a coat of paint, and no one would be any the wiser.
Animals are such agreeable Friends.
They ask no Questions. They pass no Criticisms.