Add all the fields to view automatically in csv export
This might be a really stupid suggestion but why dont you just edit the view and add all the registration fields manually. The view will have empty cells for fields thats not a part of the registration type at a specific row, but thats something you'll get anyways.

Another way to go is to skip views alltogether and export data with a module of your own using the entity api. You aparently are writing a module to override view fields above so you have already started down that road (so to speak)