Wiring stapled across bottom of beams? Can a running board be attached and the wires secured to the running board?
1/2” plywood is legal and would work great in this case pop all the anchors slip the wood in place and everything will be to code  NEC exhibit 334.1 has a great example of exactly this.
Your example is a good one but I tend to go directly to the code book as it is the document most jurisdictions use in the US and that is my location.