I would take one of two approaches to this.
- Create a Custom Table in Kentico that holds the additional fields you need and a field for record GUID from the class table in the Polls app.
- Similar to #1, except using a custom module class instead of a custom table.
You would then need to clone any relevant web-parts and add custom logic to join to your custom table or class.
You could also create custom queries on your custom table/class to aid in retrevial of relevant records.