[keeperofdakeys]

For a new transport layer protocol like QUIC, this can work. However when you start talking about IP, you need to update/replace basically every device on the internet. If a device in the path doesn't know about the extended address space, that packet probably can't reach it's destination.

[FullyFunctional]

? You have to upgrade the software on all devices to move to a larger address space. That's understood. What we are discussing here is the added complexity of the configuration. Updating the software is easy by comparison.