Thanks for the additional context. Setting a custom default model behind Standard and Premium isn't planned right now, but we've logged the request. 🙏🏻
Each of these auto models is an ordered list of candidates that Dust maintains and publishes in the docs, and it resolves to the first model enabled in your workspace. So while you can't pick the model directly, disabling providers on the Model Providers page does change what Standard and Premium resolve to. For agents you build centrally, you can also pin a specific model.
Out of curiosity, if you could set them today, which model would you put behind Standard and Premium, and why?