While this is a wonderful article, the lens he proposes is extremely limiting - it will only work with tiny sensors, or will be exorbitantly expensive to source.
You can already see some vignetting and halo on this Seek Reveal, which has a very small sensor. If one attempted to make a telephoto lens for something like a FLIR Exx or Txxx camera, you would be in a world of hurt, with just the lens elements blowing through $1000 right away - the point at which the original telephoto lenses can be found second-hand, or sometimes even brand new from the manufacturer.