There seems to be a variance between "It's OK to just give out a /64" to "You better be thinking about giving out a /48". I can live in those boundaries and am most likely fine with either. I'm leaning toward a /56 for regular subscribers and a /48 only for business or large scale customers, and undecided on dial-up. How does this sound?
The starting point is to give everybody a /48 per site. If a business customer has 3 sites, then give them enough space for a /48 for each site. Could be 3 /48s or could be a /46. But, if you have a lot of residential customers, it is quite reasonable to give them a /56 per site instead. Be prepared for some customers to ask for two /56s because they have a granny-flat or in-law apartment in the house. Also be prepared for some to ask for a /48 because they are running a business at home, or they are technical types who have a their own home network lab. Your plan for /56 to residential subscribers and /48 to business subscribers sounds perfectly fine as long as your systems have some way to accomodate that grey area, either by recording a /48 against a residential subscriber or counting them as a class of business customer that pays a residential rate. Charging a customer extra for more IPv6 addresses just will not fly in a competitive market. --Michael Dillon