Hi Matt,
You're on the right track with the `state_names` attribute, but they simply haven't been implemented in a general way for SARIMAX yet (for example, the `UnobservedComponents` model has more helpful values `state_names`).
For SARIMAX, the lowest hanging fruit would be to do something better for the AR(p) case, since it is straightforward, but as your example shows, in even the ARMA(p, q) case it quickly becomes difficult to figure out what a useful "state name" would be.
So, unfortunately the answer is that we do not have any helper functions right now that would provide this information. But if you end up creating something and would be interested in adding it to Statsmodels (even if it just covered a subset of cases), that would be great!
Best,
Chad