An interesting concept! At present I am working on rolling stock and locos in HON3 but I see the charm. For me the issue is mostly the mechanicals of locomotives so I have gone the rather expensive way of real HON3 Locos. As I am a 3D printer, I can and am printing items in ant scale I desire and currently creating what seems like way too many freight cars. But I could have done these in any scale as I don't use kits and commercial parts except for the aforementioned locos and trucks/couplers. For using std HO as 3'NG the correct scale would be 1:55.4 and certainly I could construct in this scale but this would in my case cause a considerable increase in the size of the layout.
A fun idea and good to think out of the box, after all one can do whatever they want on their layout!