First CCR's yes I know that DIR don't use them, and this is why I was saying most of us do use them, and have used them for so long without anyone killing themselfs on them ( in Europe yes there has been a lot of death, but in Australia we had no death on CCR'S ).
Helmets: apart from some regions which have crystal clear water, other places that we dive most have very dirty water ( 1 or 2 Meters ) , very sharp rocks, easy to smack your head nop matter how carefull, also we mount back up lights on them, and I think most wear helmets because of this. Well I do now as well, it makes easier to see when you need both hands to do something. I never had problems with deploying the long hose with teh helmet on, I suppose it's a personal thing really.
Lights, I use a greenforce light whixh is an 18W HID and has a very thin battery pack. I mount it on the inside between the wing and the cylinders, or between the twins, it has a bag that you put the battery pack in. What you find with the Australia cave divers a lot make their own lights, so it varies with shape and sizes, but a lot use canisters, and do hip mount them as well as butt mount them ( nothing new here ) .
Independent twins: the reason they popular over manifolds, a lot of sites require to carry cylinders one by one, but also the older divers have this thing against manifolds, but I love them, and suffer a bit extra carrying the twins myself , but better than independants. You will find more and more people are using them now here , mostly for deep diving that caves.
I have adopted a lot of ideas from DIR setups, I don't knock them down completely, it's just the attitude of DIR divers just wrong. But anyway I hope this gives you a little idea of my setup, let me know what else you would like to know.