You may want to have a look at the following a proposal, EzIP (phonetic for Easy IPv4) that we submitted to IETF:
The EzIP utilizes the original IPv4 protocol standard RFC791 and the long-reserved yet hardly-used 240/4 address block to expand the IPv4 pool by 256M fold.
Basically, this approach will not only resolve IPv4 address shortage issues, but also largely mitigate the root cause to cyber security vulnerabilities, plus open up new possibilities for the Internet, all within the confines of the IPv4 domain. In fact, this scheme even may be deployed "stealthily" for isolated regions where needed.
Abe (2018-07-19 22:29)