How are other providers approaching dial-up? I would presume we are in the same boat as a lot of other folks - we have aging dial-up equipment that does not support IPv6 (3com Total Control). Our customer base has dropped quite a bit, and we have even kicked around the idea dropping that service and forcing customers to purchase broadband service or go elsewhere.
Separate these technical issues from IPv6 allocation plans. If you intend to continue running an ISP in two years from now, either make a simple plan and allocate a /48 to every customer site, whether or not they are currently taking an IPv6 service from you. Or, take the slightly more complex plan and allocate a /56 per site where it is known for sure, 100% that the site is a private residence. If it is not, or there is doubt, then allocate a /48.
I expect we won't invest any more into dial-up equipment, and when a dial-up customer happens to ask about IPv6 (if ever), we'll strongly encourage them to move to broadband, and as a last resort manually configure a /64 tunnel to them.
You might use up a /64 for the two tunnel endpoints, but be sure to allocate the customer at least a /56.
What are other providers doing, or considering doing?
In general, big providers are not going to attempt to cope with any older equipment that does not fully support IPv6. But small providers will be rather innovative and try things like your tunnel suggestion. After all, if Hurricane Electric can run an IPv6 tunnel broker, why can't you? --Michael Dillon