At the risk of posing a conflict of interest, I say its doable. That's pretty thin. Your not asking too much.
Sometimes I state the obvious. That may be the case here. The problem with cutting brass isn't when its cutting, it when its not cutting that things get cooked. Your operator has to watch it, stand right there when its being cut, and make sure the be beam is going through the material. If it looses its cut, that's when things get ugly in a hurry.
Again with the obvious. If there is money to be made cutting brass then I would do it. If the owner is willing to pay someone to stand there and hover over the stop button, if he/she understands that if there is serious reflection, yes, the output coupler or the focus lens could burn up. If the profit is greater than the cost of clean up, then go for it. We don't want all those fancy fiber lasers steeling our CO2 work.