Here's what it would look like:
1. An IPv6 client with a globally-scoped IPv6 address (the Source) requests an IPv6 multicast address from the service. The address is valid for a particular amount of time, unless renewed. The address can be renewed indefinitely.
2. Other IPv6 clients (the Clients) are given the multicast address and join that multicast group, using the (S, G) method.
3. The Source sends packets to the multicast address and the Clients receive them.
I have no idea what the billing would look like, perhaps traffic sent over the channel? I just know I would use this service if it existed.
Thanks!
Also, the cost of a new multicast address should be negligible (e.g. $0.01). Instead, charge for incoming traffic on that multicast address from the Source.