Pardon me if you're already getting notifications about this, but we're having a lively discussion over on discuss.folio.org about this issue of whether and how to come up with a list of MARC fields to be included in the reporting system (https://discuss.folio.org/t/listing-marc-fields-for-reporting/1335/7). If you haven't been following it, you might want to give it a look.
(Sending this because I can't tell who might be tracking the reporting sig discussions. Please excuse the duplication if you're already aware of all this.)