What you are looking for
People who have done this across financial services, healthcare, retail, SaaS. People who can pattern-match your situation to the dozens they have seen before.
They are not going to run a Big 4 reorg. But they can tell you when you are not ready. They can tell you when you are solving the wrong problem. They can say "I saw this exact thing at a healthcare company last year and here is what happened" — because they have the pattern library that only comes from doing it at scale across multiple industries.
What they can tell you
When you are not ready. When you are solving the wrong problem. What has worked at similar organizations. What has failed and why. That is the conversation worth having.
Why this matters for your evaluation
A vendor with one overbooked solutions architect stretched across forty accounts cannot give you a strategic conversation. They can give you a demo and a proposal. Those are not the same thing.
The Field CTO ask is not rude. The vendor wants to accelerate your adoption just as much as you do. Getting the right people in the room from the start helps everyone. If they tell you that access is a premium service tier, they have answered the question of how strategic they intend to be with you.
Ask directly
"Can we have a Field CTO or Principal Engineer join the initial call?" That is the ask. Watch the response. It tells you everything.