I guess I'm confused with everyone calling this a small cage....? It's bigger than almost every hen house I've seen and bigger than any rubbermaid container I've ever seen. It's 40x18 or something like that. That's too small? It's only slightly smaller than the troughs they keep 100 babies in at the feed store.
The troughs used in feed stores are used as very temporary housing - *most* chicks sell out before they even reach the 1 week mark. Those are not set up as long-term brooders to be used to take the chicks to the point of being able to move out of the brooder and are not a good reference point to build an argument as to what is a good setup for such. The simple fact is that animals can survive less than desirable conditions (such as inappropriate housing), but the goal as a responsible keeper should not merely be to have them survive, but to provide what they need to thrive - such as an appropriate amount of space.