With comics there is the eternal need to keep things simple because they must be re-hand-drawn for every frame. That is not as much a requirement with CGI matter such as Xcalibur
http://en.wikipedia.org/wiki/Xcalibur

It seems that in producton of Rogue Trooper there was no decision about standard kit.

And there will be those who say "follow the majority of comic images or it won't be realistic".

But see http://en.wikipedia.org/wiki/Diving_regulator#Demone_regulator