I absolutely hate mesh masks/goggles, they drive me crazy. Yeah they don't fog but neither do a good pair of ESS goggles. Looking through the mesh gives me a headache and there's the shatter/shrapnel problem as well. I'll stick to my ESS goggles thanks.
As to mouthguards, I assume the rigs used for boxing or football would work fine. The only problem with those is you can't talk.