This sounds like only way I can get results is by installing water mist sprayers (which is easy to do) on the bike and leaving evaporation cooling garments alone altogether. I'd gladly simply avoid such temperatures, but I am looking into scenario like I had last year. We did 1 week great riding in Norway - no heat problem :)
Then we hit piece of highway (about 800 km) back to Belgium and - guess what - +35 celsius, totally unexpected by anyone, bright sun and all this on concrete layered autobahn ( surface was so hot it was incredible) and traffic jams - this created crazy effect. I never was that hot in my life (except in Andalusia in Spain in July - there it was worse) despite I was lane splitting like crazy. The only positive side - lot of girls in cars drove in bikinis (unusual for Germany indeed) which allowed me to shift my concentration off heat
. But seriously - I was pouring water on my gear all over on each fuel station yet still felt horrible - you know, "hot fan into face" kind of weather?
So, idea is not to use it for radial driving as such - I have specific gear for that, but to use it when you caught in long trip by hot weather.