SSG Message
Perhaps a solution to the problem would be a Featured Small Giant Game Message added to the Inbox? Reusing the code might save time. Might not.
News
We cannot send mail ( good call Devs ). I noticed the Devs added expiration dates to the mail messages.
Maybe replace the message system with a News section like Niantic uses for Pokémon GO where the Devs control the displayed “News”, it’s order, and it’s removal.