Ever since I discovered the beauty of a reflective trekking umbrella, rain kilt and dirty girl gaiter from people who hiked the Pacific Crest Trail, as well as hiking shoes, I adopted the trekking umbrella and hiking shoes, have not had the chance to use the other two, but would considered it for primitive. No route on the camino is harder than PCT through hike from the unforgiving desert at the Mexico border to the cold wet Canadian border, if it works there, it is really tested.
I would not use this trekking umbrella hiking in the pacific north west, however, Southern Spain or any where with potential 35+c degree, I would not go without. The real temperature on the exposed shadeless dirt road definitely was a few degree higher than the forecasted temperature. The constant shade provided by the umbrella, on the contrary, reduced the temperature by a few degrees, I could sit down any time, any where I needed without looking for a shade which was hard to find and it also reduced my need of water consumption significantly. Last but not the least, it was also handy using as a cover at roadside restroom stops. The benefits of it totally justifies carrying this <200gram for me.
Another option is using a really cheap regular folded umbrella in the south and leave it behind at Salamanca or anytime it gets broken. Same method to attach to the backpack for hands free.
Also can consider rain kilt, rain jacket and bag cover combination to replace poncho and rain pants. The rain kilt was much lighter than a pair of rain pants, maybe only 3 Ozs, can't remember.
As for getting up at 4am on the VDlP in summer, the day light was around 6:30-6:45am for July/Aug. Have met people leaving at 5am, definitely not daily. Have not heard or met one left at 4am. The hottest time of the day is around 4pm to 6pm, from 6am to 4pm you got solid 10 hours.
In addition, if one leaves at 4am, probably will not get any service before 10am, that is 6 hours without a cafe or shop, even if there is one there. I remember on the Frances, if 10km without any service, it was a big deal. On the VDlP that is very common, even 15km without service is not uncommon.