There is an easy solution -- do not allocate less than /16s.
This would relieve InterNIC from caring about IN-ADDRs
(and will do good things for routing, too).
All ISPs receiving /16 prefix blocks from the InterNIC will be responsible
for maintaining all IN-ADDR.ARPA domain records for their respective
customers. The InterNIC Registry will only be responsible for the
maintenance of IN-ADDR.ARPA domain records for those CIDR blocks with
prefixes longer than /16 issued directly from the InterNIC.