John, I’ve worn sandalls as my only footwear on 2 AT & 2 PCT thru-hikes. At least a handful of people have hiked the AT barefoot. Ankle support is an interesting topic b/c most shoes, even lightweight boots cannot withstand a severe roll or twist - its kinda a false sense of security. It seems that when you wear running shoes or sandalls, you naturally tend to place your feet more carefully, which helps reduce the twisting. A light pack helps as well.
In terms of rubbing/blisters, i’ve found that wearing the sadalls very loosely helps - i set the straps on my Teva’s as loose as possible. I’m currently about 850 miles in on a PCT thru-hike and i don’t have any blisters or other problems with my feet so far. (i use neoprene socks in the snow)
Good luck with your Amphibious shoes & Happy Trails!
freebird