I'm for 1 sec cooldown and 5-6 seconds of fire immunity,I find that one of the more interesting aspects of engineering is considering the damage type. Making that hard choice between chemming the fire and malleting the stacks off, or barely managing to mallet the armor back up against a gatling. Extinguishing between cooldowns makes it a boring and braindead weapon. With atleast a second of cooldown you actually have to put a lot more consideration as to when you're going to mallet. Ext shines in situations where you have a variety of fire and actual damage attacking your ship, but prolonged engagements kill it. It could do well against a gat banshee, which is basically a less efffective version of gat flamer, which the ext cant handle, therefore its underwhelming to use. A one second cooldown would make extinguisher even better at something it's already good at over the chem: Shaving off fires and tanking damage at the same time. Whereas chem is more of simply tanking and less extinguishing long as you play it right.