I believe if they didn't aggregate it across the subs, they wouldn't have enough capital to actually compete on some of the sports... Its a tactical decision on their part to force subsidisation of the sports channels for Skys benefit so they can bid higher or bid for more sports.
I dont follow what you mean. Sky buys the sports rights it currently buys from each of the rights owners. Sky chooses to aggregate them to the subscribers.
That does end up being a sizeable cost per subscriber, but you get a lot in return. If you follow three sports big time and enjoy others, its not bad value.
It would be very messy to have an F1 channel, MOTOGP channel and so on, each at a smaller cost. I think thats what you mean?