My team is using Constituent Additional Information fields as a universal field: we ask why participants register to our events for every event via Survey then we set the survey response field to one of Constituent Additional Information field and view constituent's answer on the constituent level.

Since each survey has different IDs and question and response ids in Web Services, it is hard to map data into our core database but if Constituent Additional Information fields which we are using as universal fields are available in Web Services, the data integration process will be much simpler.