One other item:
Neither this, nor many NAT I-D's, address the particular
issue of sourcing IP addresses not assigned or owned by
the host/gateway, e.g., as they affect the standards
of RFCs 1122, 1123, and 1812.
If a device creates (rewrites) IP source addresses with
addresses not its own, it would be useful to see a section
specifically addressing the resulting implications.
Joe