Ya know, it's just physics. If the ratios of swept area, pressure, and vehicle weight are correct Mr Newton doesn't care what method is used to achieve it. If they're not, then neither air nor hydraulic actuation will help you.
I haven't paid a lot of attention to the workhorse brake issue on the forums. But pins and pistons are a cost trade. Most street vehicles use sliding pin but look at any retrofit brake kit and they'll have pistons on both sides, sometimes as many as 4 on each side. Much more expensive but more consistent and reliable, less affected by dirt and corrosion.
Phenolic pistons? A good friend of mine had those on a 1982 Ford E150 and they melted on a long downhill in the rockies. I guess it doesn't surprise me that companies will continue to go down that path as materials get better.