[BizarroLand]

So, in my IPv4.1 suggestion, every address you currently know would work perfectly fine.

But then so would AE1.224.78.BC2

Sure, a little harder to remember maybe, but adding nearly a billion times as many IP addresses would alleviate the strain on the internet, be backwards compatible with IPv4 (but not forwards compatible, so most interior/home networks would use either a NAT or have a software ipv4-4.1 bridge software)

It would also be much more similar to IPv6 which would ease transition to full IPv6 if the human race survives long enough to ever make the jump. IPv6 is just more hexadecimal after all.

[Dagger2]

Wait, you wanted to extend the text representation of v4 addresses? That's not a thing that exists in the protocol. The addresses are in binary in the packet format and in all data structures, so any extension of the character set in the text representation has to be implemented by increasing the bit length of the addresses.

I don't know why you think this is "inherently backwards compatible" yet think v6 isn't. It's just as backwards-compatible as v6 is.