I wish the article had sample photos. I have doubts about whether a better lens can make much difference on Instax Mini film. Also, why waste a 4" x 5" lens to expose a 46mm x 62mm image? A medium format lens would be a closer fit, but I guess a hacker uses the parts that he has lying around.
I've also seen a workaround to expose Instax film in a Rolleiflex or other TLR with a polaroid back, and polaroidconversions.com offers conversions of Polaroid cameras to use Instax films.
To my mind the bigger benefit rather than a better lens is regaining manual exposure control. I enjoy instant prints and use Instax wide and mini (with an SP-1 printer) quite a bit. The "problem" with the Instax cameras is they're fixed focus, fixed aperture (f/14 at least in the case of my Instax 210), and automatic flash. Personally I'd love a manual-exposure Instax camera that has facility for on and off camera flash synchronization.