Possibility of downgrading into null-cipher at the sender's discretion

Hi. After going through the new AEAD specs, I realized the new chunked format could allow for encryption-downgrade at some point in the middle of a live connection. For example, a server may choose to only use AEAD for the handshake part of the TLS/SSL payload, but downgrade the encryption to null-level after TLS-handshake completion. This can be signaled with "encryption payload lengh"=0 in the
[encrypted payload length][length tag][encrypted payload][payload tag] part, indicating that all the upcoming bytes are raw-stream without encryption.

This is especially helpful when the clients/servers are on low performance boxes like openvz vps or mips routers, and encryption overhead considered non-trivial. End-points could use policy like "drop encryption after 4kb for port 443".

Any cons?

Start with the proposed chunked format in the issue body and review the referenced AEAD and TLS/SSL assumptions. Determine whether a sender-controlled transition to raw-stream bytes is an intended protocol change and document the security, interoperability, and policy requirements. Done means the proposal has a resolved design and implementation scope.