A newborn baby is not a CPU+motherboard which just needs to grow the other peripherals and BAM it all just snaps into place, nor is it a tiny adult with fully functional tiny appendages.
A newborn needs to develop all sorts of skills - starting with breathing patterns & sleep patterns, not to mention feeding. Yes, these things become automatic pretty quickly; however, the baby needs to "bootstrap" itself from the absolute basics provided by reflex, iteratively, to more and more complex tasks - it cannot start in the middle of the "technology tree," to use a metaphor from strategic games, as it would lack the underlying capabilities. Muscle coordination (in other words, developing the neural activation patterns whose existence you're presupposing), sensory input (movement w/o vision, very useful) and cross-referencing the inputs/outputs comes much, much later.
Now, with a 6-month-old, that exoskeleton of yours might be actually workable (in theory) - but a newborn? No way at all; your view of human biology is rather cartoonish: we're not starting out with a complete brain which just needs some muscles, the brain develops alongside the rest of the organism.