Solid overview. One thing I'd add to the selection criteria: whichever model you pick, it's worth verifying periodically that the endpoint actually serves what it claims — especially with third-party gateways. A small behavioral smoke test (a few fixed prompts at temperature 0, diffed against the official API) catches silent downgrades that benchmark tables never will. Model choice is a starting point; verification is what keeps it honest.
Seven
Well said — "verification turns model choice from a guess into a process" is the right shape. The one thing I'd add to a recurring smoke test: record the model id the response reports, not just pass/fail. When the endpoint changes what serves a request, that field is usually the first and only place it shows.