Well, you can delegate these as 128 individual zones. With a little
bit of automation to help, it may approach practical. You can
delegate a single domain name in the limiting case.
But this doesn't really save anything in terms of the amount of work that
has to be done by the NICs and probably increases it, as when the ISP's
clients want to be primary for their IN-ADDR.ARPA domains, the delegation
records will have to be updated to list extra servers.