If the user selects no weather station (which should be a possibility), then the sensor entities that depend on this weather station being configured should simply not be added to Home Assistant.
Stretch goal: if the entities already exist for whatever reason, simply delete them. Not sure how to do this!
The weather station that the integration asks about when configuring, does not necessarily have to be used. In other words, it should be optional. https://github.com/Rudd-O/homeassistant-meteoswiss/issues/4 hints at this.
If the user selects no weather station (which should be a possibility), then the sensor entities that depend on this weather station being configured should simply not be added to Home Assistant.
Stretch goal: if the entities already exist for whatever reason, simply delete them. Not sure how to do this!