Perhaps some kind of Trex or Trex-type engineered product? There are a huge variety of configurations, colors, looks, thicknesses etc. including many tongue and groove variations, or even 12" wide "boards".

The kind you decide on will depend on the climate since it does have some noticeable "give" during extremes of hot and cold.

Don't you need to do a membrane, with a floating floor over it? What does your local building inspector and code say? Hope all the wood is pressure treated, and don't forget to divert the draining water somewhere. That is a very narrow walkway. Can you sister to the cantilevers and add 1-2 feet while you're still in the framing stage? It will make a big difference later. Do a search for waterproof/watertight decks. There are new systems on the market and all of them work with their own specific membranes and flashing systems.

usually the floor is done first so the integral flashing can wrap up the wall and under the installed door. On top of your waterproofing you could put whatever you wanted. you need to get a professional out there!

I agree you need a fully self adhered membrane and it needs to go up the wall under the stucco and into any doorways. We put them in before stucco with the roofing. Your best bet is to get a roofer that is familiar and experienced in low slope and membrane roofs to give you guidance and discuss what your options are now that the stucco is installed. After the membrane is in you can float a finish material over it such as tile. I also suggest you attached your guard rail to the fascia, if it is strong enough, to avoid compromising the membrane.

Thanks so much! The rail consideration is one I would have overlooked. Is there a product you've had success with in this type of application?

HI -- There is a product called Dura Deck which is a full sheet goods product for such places . Or some high end out door carpeting has come a long way since the grass like turf .