five, I believe that one of the benefits of the free school scheme is that schools that offer alternative approaches and methodologies now have a place in the state-funded system. I only use Summerhil and Montessori as examples of alternatives to the traditional classroom and exam focused methodology, Summerhill because it's already been mentioned, and Montessori because it's vaguely understood across a large audience. Under the free school system, there could be publicly available montessori or summerhill-like schools. (Though I think there are actually several Montessori schools in the state system.)
I don't see how a traditional classroom methodology and a montessori-like methodology are compatible within a single school, again as an illustration. If you were to set them up in the same school, they'd be such diverse offerings that the two sections of the school for all intents and purposes would behave as two separate schools. They would need separate heads! So why not have two separate schools?
I certainly believe that a child could be both a gifted musician as well as scientist, most of us would. And I wouldn't be personally inclined to send my dc to schools with a specific focus on content, unless of course they were really keen to do so.
I do think the question of curriculum CONTENT and teaching METHODOLOGY gets very confused in these discussions. While I think a conventional comprehensive could and perhaps ought to offer a wide range of CONTENT at different levels, I don't see how it can offer a range of METHODOLOGY. I hope this addresses your question of why I think numerous small schools are better at addressing diversity than one big school. I also have a prejudice toward smaller schools, as I see them as more flexible and responsive, compared to larger schools, which I perceive as more cumbersome and bureaucratic. Whether this prejudice stands up to scrutiny is another matter.