The question of this thread relates to technical diving, in which redundant gas is a requirement.Shouldn't the gas guzzler be forced to bring his/hers/it's own redundant gas -- perish the thought, a pony?
This issue illustrates one big difference between recreational and technical diving. Except for unusual cases, gas matching is not involved much in recreational diving, and gas guzzlers frequently carry more gas so that they can stay at depth as long as their companions.That does not work in technical diving. In technical diving, the gas planning depends upon the diver with the least gas. One day when I was in cave training, we were accompanied by an instructor intern. My instructor and I were diving cave-filled LP 104s. The intern brought LP 85s, and my instructor was clearly annoyed that our dives would be limited by the intern's gas supply.