Does the question for the "person entering survey" already exist in the other 3 surveys but just as a text field and you want to add the drop down, or there is no similar question?
If there is no field for this question at all, you can add it to your survey and re-publish, and the new field and question type will be added to the feature service and survey, without effecting existing data. This is a new enhancement in latest version of Survey123 Connect, it no longer required recreating feature service for adding new fields.
If the field already exists but only as a text field, you can change it to a select_one, and add the choice list, provided the field length is the same (255 by default) you can republish the survey and it will be updated in the survey. The feature service will not be effected as the field type and length is the same for text and select_one questions.