Hey team, thanks for the detailed feedback on the PR. Before investing more time we wanted to share what we found in the codebase and get your guidance.
On the "over-engineered" point
gcpvertexai.rs in the same codebase solves the same structural problem for GCP Vertex AI: one endpoint, multiple publishers, multiple API wire formats. It is 1 226 lines (836 + 390 for formats) and is already merged.
Azure Foundry is the same situation with a wider surface: