Sidetracking: actually we tried that (added criteria for the first IPv4 allocation) - result? People got 'me a handful of /24 PI networks, paying some small saving on the address space side with more pollution on the routing table size. So we changed it back.
When we transition to IPv6, we lose any benefits of the savings in IPv4 addresses, however, the penalty of pollution in the routing table is multiplied. Savings in IPv4 space, do not carry over into IPv6. That is why we lose these savings. But the size of the routing table increases by 4 times therefore requiring 4 times as much RAM and 4 times as much time to send/receive full routes. No doubt one could apply some weighting factors and conclude that the overall penalty is multiplied by less than 4 times, however the fact is that the penalty is greater. Therefore, is it false economy to have policies which put IPv4 address space conservation higher on the agenda than routing table size conservation? Policies interact, including interaction between IPv4 and IPv6 policy. With IPv6 we can afford to be generous. --Michael Dillon