First, I'd like to point out that throwing a gas trap directly on top of someone causes it to not trigger for several seconds. I've thrown barrels in the heat of a fight to try and help save me just to watch the enemy run around it and it doesn't trigger. I'm not sure if there is a delay or what, but if someone is within radius of a normal trigger, it should trigger as soon as it inflates.
Second, mustard gas can be more explosive if its heated. If the gas barrel is near/by a thermite, the barrel should heat up and a bigger/longer explosion should occur. Maybe similar to the ultimate? Give caustic a torch and let him pre-heat his barrels for added fun. They heat up to a certain temperature (right before explosion) and slowly the heat bleeds off over time taking them back to a normal barrel. The intensity of the barrel explosion could depend on its heat level.
Allow caustic to sabotage unopened loot bins by 'attaching' a gas trap to the bin that triggers when the bin is opened. I think this would be hilarious! Crypto should be able to defuse the trap with his drone and wraith should be able to warn people of the "loot bin trap".