There are only 2 reasons that I can see to write a special policy. One is to encourage ISPs to assign /56 prefixes to customers, not longer ones like /60. Or /60s vs. /64s. I think you may be a little optimistic if you think that /60 is the low end of the totem pole here.
I don't believe that RIR policy should ever encourage ISPs to assign customer sites a prefix longer than /56. In fact, we really should discourage assigning anything other than a /48 or a /56 because part of the benefit of IPv6 comes from giving the customers a spacious number space in which they can subnet. This also allows for greater portability, i.e. I can switch providers without changing my network architecture, or I can relocate to another country and know that I will get the same prefix length assignment.
Case in point is that when Free first offered its IPv6 service, it did so within the /32 it had by giving /64s to all its customers. A few folks like myself complained, and they changed it only because they were able to get a large enough allocation from RIPE (which they had to go back and ask for). If that had not happened, it's not like Free would have ripped out its entire DSLAM infrastructure and upgraded it to offer a /60 or /56. The choice would have been /64 or nothing. Period.
The point is that it did happen. RIPE did give them enough address space to offer customers more than a /64. That is the way things should be because there is no shortage of IPv6 address space. In fact, RIPE should refuse to give ISPs an allocation so small that it forces them to offer customers anything longer than a /56 prefix.
I'd be perfectly fine with no new policy, as long as ISPs, even relatively small ones, do not delay IPv6 deployment over lack of obtainable space.
Yet another reason why RIPE should be liberal with IPv6 space. In IPv4, a /32 will number one host. In IPv6, the same prefix will provide many ISPs enough address space to last them 20 to 50 years. In IPv4, a /24 is something that you assign to customers and a /21 is a small ISP. Why should we be more restrictive in IPv6? I can see no good reason to not hand out ISPs a /24 or a /21 if they need it to make their IPv6 access service work. Even though my employer, a rather large ISP, expects to fit within a /21 with native IPv6 services, I do not see the need to require every other ISP to use their IPv6 allocation as efficiently as we do. Cost efficiency is more important, and if a medium sized ISP needs a /21 in order to get their IPv6 service rolled out faster, then I believe we should give them that /21. The sooner we get the IPv6 transition into full gear, the better it will be for all of us. Network effects demand that we help our competitors by removing any barriers that limit them or slow them down. --Michael Dillon