IPv6 is the only way forward

The only lesson to learn from IPv6 deployment is that if there's a workaround available and the world isn't burning, it'll take 30 years from initial design to actual adoption. So if you went out and took 10 years to design IPv7, it'd likely take until 2070 for it to gain some adoption. This is because big network hardware is costly and has very long replacement cycles.

IPv6 was already designed as a lessons-learnt protocol from IPv4 issues. The header is greatly simplified and it's more hardware-friendly, it incorporates the required features into the protocol and leaves extensibility as an optional add-on that doesn't slow down routing packets, all the while granting an infinite address space.

Like

> Addresses in this group consist of an 80-bit prefix of zeros, the next 16 bits are ones, and the remaining, least-significant 32 bits contain the IPv4 address. For example, ::ffff:192.0.2.128 represents the IPv4 address 192.0.2.128. A previous format, called "IPv4-compatible IPv6 address", was ::192.0.2.128; however, this method is deprecated.[5]

* https://en.wikipedia.org/wiki/IPv6#IPv4-mapped_IPv6_addresse...

Or:

> For any 32-bit global IPv4 address that is assigned to a host, a 48-bit 6to4 IPv6 prefix can be constructed for use by that host (and if applicable the network behind it) by appending the IPv4 address to 2002::/16.

> For example, the global IPv4 address 192.0.2.4 has the corresponding 6to4 prefix 2002:c000:0204::/48. This gives a prefix length of 48 bits, which leaves room for a 16-bit subnet field and 64 bit host addresses within the subnets.

* https://en.wikipedia.org/wiki/6to4

So you have to ship new code to every 'network element' to support your "IPv4+" plan. Just like with IPv6.

So you have to update DNS to create new resource record types ("A" is hard-coded to 32-bits) to support the new longer addresses, and have all user-land code start asking for, using, and understanding the new record replies. Just like with IPv6. (A lot of legacy code did not have room in data structures for multiple reply types: sure you'd get the "A" but unless you updated the code to get the "A+" address (for "IPv4+" addresses) you could never get to the longer with address… just like IPv6 needed code updates to recognize AAAA, otherwise you were A-only.)

You need to update socket APIs to hold new data structures for longer addresses so your app can tell the kernel to send packets to the new addresses. Just like with IPv6. In any 'address extension' plan the legacy code cannot use the new address space; you have to:

* update the IP stack (like with IPv6)

* tell applications about new DNS records (like IPv6)

* set up translation layers for legacy-only code to reach extended-only destination (like IPv6 with DNS64/NAT64, CLAT, etc)

You're updating the exact same code paths in both the "IPv4+" and IPv6 scenarios: dual-stack, DNS, socket address structures, dealing with legacy-only code that is never touched to deal with the larger address space.

Deploying the new "IPv4+" code will take time, there will partial deployment of IPv4+ is no different than having partial deployment of IPv6: you have islands of it and have to fall back to the 'legacy' IPv4-plain protocol when the new protocol fails to connect:

* https://en.wikipedia.org/wiki/Happy_Eyeballs

"Just adding more bits" means updating a whole bunch of code (routers, firewalls, DNS, APIs, userland, etc) to handle the new data structures. There is no "just": it's the same work for IPv6 as with any other idea.

(This idea of "just add more addresses" comes up in every discussion of IPv6, and people do not bother thinking about what needs to change to "just" do it.)

> If IPv4 were more painfully broken then the switch would have happened long ago.

IPv4 is very painful for people not in the US or Western Europe that (a) were now there early enough to get in on the IPv4 address land rush, or (b) don't have enough money to buy as many IPv4 addresses as they need (assuming someone wants to sell them).

So a lot of areas of the world have switched, it's just that you're perhaps in a privileged demographic and are blind to it.

UTF-7 was possible because there was an out-of-band mechanism to signal its use, "Content-Type: text/plain; charset=UTF-7":

* https://datatracker.ietf.org/doc/html/rfc2152

What's the OOB signalling in IP packet transmission between two random nodes on the Internet.

Sure everything above IPv6 have, but it took years and years of screaming to get it.