Cutting with no eye protection...

[Rambozo]

Wouldn't an auto darkening helmet that has adjustable shade control from 6 to 13 work well for plasma cutting?

It could. 6 might be a little dark for some people. The grind mode of many are about 4 which can work, too, but is a little light, for most. How bright your surroundings are have an effect, too. Everyone is a little different. However, the helmets that have cutting modes to go from 3 or 4 to 8 or 9 will cover whatever you need. That's the great thing about adjustable shades. No more mixing sunglasses with #5 shaded face shield to get it just a little bit darker for some bright O/A work.

[everlastsupport]

I agree, 6 is a bit dark "for me" as well. We have #5 glasses and #5 full face shields. The welding helmets are a little klunky for cutting and O/A "for me" as well. As Rambozo said, everyone is a little different. You need to find what works for you.