I am somewhat of a heretic in that I do not believe cotton is inappropriate on the
Meseta, in the
Summer. Both of those qualification are important A fuller explanation is here:
https://www.caminodesantiago.me/com...id-not-for-a-summer-camino.31137/#post-269857
That being said, I would seriously rethink his clothing. First, as explained in the longer post, at most I would have one set of quick-dry nylon and one set of cotton clothing (not all cotton, as here). I understand the Australia is mostly very arid and dry. Cotton works great in that climate, and the meseta in the summer can feel similar. But the mountains on either end are much wetter (the rain in Spain falls mainly . . . . in Galicia and the Pyrenees; don't believe My Fair Lady). Cotton is great in the arid, dry areas because it retains water, leading to an evaporative cooling effect (think of a cheesecloth dipped in water and held before a fan). For exactly that same reason, cotton is very bad, and can even be dangerous, in wet, cooler climates. It never dries and cools your body to the point it can lead to real chills and sometimes even hypothermia, even if the air temperature is well above freezing.
And cotton socks are a total disaster in any hiking environment (except the treadmill at the gym).
I did not like quick dry nylon very much on the meseta in July, but if I was planning the sort of epic trip he has in mind, I think I would take take only quick dry nylon. It will get him through more of the environments he is planning to encounter (particularly the UK, where it is damp; and then staying in Europe through the fall).
I also think the convertible pants are generally too heavy, but I'd take only long pants and long sleeve shirts for sun protection (I saw some epic sunburns on people walking the Camino in shorts or short sleeve shirts). I hardly ever removed the legs on my pants during my Camino.
Also, I'm not sure why a poncho and goretex rain jacket. A poncho would probably work just fine for the Camino, but I'm not sure I'd want that for the rest of the trip. I'd probably leave the poncho and go with the jacket and get rain pants (and a trash compactor bag as a pack liner).
I'd also add a stocking hat (very light, and really helped on cool nights/mornings). I'm assuming the hat on his list is a sun hat (full brim, not just a ball cap).
For what it's worth,
Jo Jo