I have a tenured architect proposing that we stop sending structured data internally between two services (JSON) - and instead pass raw textual data spat out by an LLM which linguistically encodes the same information.

Literally nothing about this proposal makes sense. The loss of precision/accuracy (the LLM is akin to applying one-way lossy and non-deterministic encoding to the source data), the costs involved, efficiency, etc.

All just to tell everybody they managed to shove LLMs somewhere into the backend.