I would have problems if an inspector red tagged a code compliant NM job because the specs called for conduit. That is not the business of the inspector. He has no legal right to red tag a code compliant job. He can only enforce the law and the law is the legally adopted code and any local amendments. As far as the structural design, a change in materials, fastening devices, or design may very well be a violation of the structural building code. The change may result in a structure that is not code compliant and does not have the required strength, stiffness or flexibility.