I doubt this technology will work in the spinal cord. Getting nerves to grow in the peripheral nervous system is pretty easy - they do it on their own. Damaged peripheral nerve axons regrow at a rate of about 1 mm/day, so if you damage a nerve in your armpit it will take weeks to regrow all the way down to your fingertips. Getting nerves to grow in the central nervous system (brain + spinal cord) is tricky. The molecular signaling in the central nervous system actively inhibits regrowth of damaged nerve axons, but we are learning how to experimentally manipulate that signaling to allow some axons to regrow after injury. Someday we hope to therapeutically manipulate that signaling, to help patients with spinal cord injuries, multiple sclerosis, etc.
The nervous system is hugely complex, as you suggested. It is incomprehensibly complex. It is absolutely, beautifully complex. That's why I love it so much.