We'd like to add a new flag to the native protocol to allow drivers to connect using a "beta" native protocol version. This would be used for native protocol versions that are still in development and may not have all of the final features. Without the "beta" flag, drivers will be prevented from using the protocol version.
Cassandra ticket: #12142.
I have a preliminary early version of the patch here, although it might be tricky to use and / or test it.
We might want to wait until / if Cassandra patch is merged and test it against the latest version, as the change is unobtrusive (as in: everything old should be still working).