@John Alan, have you given any thoughts to the upper stage storage required to support your proposal 's large pool of Falcon cores? Think a stockpile of upper stages and payload fairings is needed near the vehicle integration facility.
Then there's the "economy" storage plan. I hear Arizona (and McGregor, Texas) still have some vacant land.
Americans have too much space.This is what other people have to deal with:https://www.google.co.uk/search?q=midland+gliding+club+hangar+photo&oq=midland+gliding+club+hangar+photo&aqs=chrome..69i57.17313j0j4&client=ms-android-motorola&sourceid=chrome-mobile&ie=UTF-8#imgrc=XkZlA9orcx2TcM%3A
Interesting idea, although I agree vertical is not necessary. Maybe a better idea is to stack the cores horizontally in decks, perhaps 3 x 3 (9 cores seems plenty.) Actually, I wonder if such a building could be built next to or even on top of the existing HIF. That way, you could also build an offloading platform connecting to the HIF. All it would require is a small coin-op unit on the side. Gwynne just inserts a quarter, pulls a handle, and a core rolls down right into position in the HIF!
You should expect to see SpaceX embrace vertical assembly buildings only with a radical redesign or new launch vehicle, if that. Ideas like the ones in this thread work fine geometrically, but ground area is not scarce, and they don't work economically.
Usable ground is quite scarce at LC-39A and the cape generally.