Some messages for Pickle should be deleted
This list is not useful, because it doesn't actually list messages to delete, nor why they should be deleted.
Ignored messages are not exported, so what harm do they make?
Optional messages: it's pointless to start deleting messages before explaining to translators why they are harmful.
Also, I see several of these messages don't have useful message documentation to explain what they do or how to translate them (or why they're messages at all): this should have been fixed before introducing such messages, but you have an opportunity now to improve the documentation before any cleanup, to reduce future mistakes.