We have the same sort of piped in feed setup for the nursurey, and also the cry room, which is actually part of the church, with a (mostly) soundproof window so you are still in church...pews, liturgy books, the whole shot (and a nice bathroom). It was very nice that they planned it that way when they built the church.
I will say I do agree at a certain point we should expect our kids to behave better if not perfectly. My 9 year old is definetly expected to stand and sit, cross herself and listen; she gets fidgety, but nothing too horrible. Nothing "the look" doesn't take care of. And I don't see anything wrong (and this is something a lot of parents of those "mid range" aged kids do) bringing a book or something to write on(my kids have a nice bible story book for instance) especially for the ones that get very tired during some of the longer parts. I think if they are exposed to the liturgy, etc, they will get the benefit even if they are not paying rapt attention to a service in a language they may or may not understand anyway. They'll pick it up.
But, please remember too, and I am not stating that this is the case with every "brat" because some are plain and simple...some kids may have other issues that prevent them from being able to cope...in which case I feel it wise to have them in as long as they can stand it, then remove to a more separate area. Examples may be Autism/Aspergers, ADD, etc. Right now my son is up to about 5 minutes. For him, that is good. Of course he is only 5, but it is a huge thing for him to stay in one place when there is so much to see and smell and hear...it's sensory overload(for him), on the few occasions I take him. So I say thank God (and the Parish) for the other options, and the pipe feed so I can at least know what is going on in service.
You're quite right that age and the capabilities of the individual child should be taken into account. Our youngest has mild Down Syndrome. Even at 8, he is not able to stay through an entire Sunday service. Our parish had a staffed nursery for a while when he was small and that was a fine thing. Then the priest said that it was impossible to find anyone to staff it (Some parishioners were dubious and wondered if it was considered a bother.) We took to 'tag-teaming' with one parent going to the earliest service and the other going to the late one with the two older children. It meant that one of us had to stop being in the choir which is at the 11 AM.
Then last December one of the choir people helped us meet a fine high school student with experience in caring for children with disabilities and who was willing to help us on most Sunday mornings. Our child adores her, she is interested in Japan and anime and other subjects that my family likes and since winter the choir has a voice back. It has been a great blessing.