My guild has our reports private and so our character profiles/summaries do not show any rankings.
Private reports do however have estimated rankings under the rankings tab. Would it be possible to display these estimated rankings on the character profile/summary pages given the user accessing the page has access to the private reports where those rankings were achieved (i.e. I could see my own and all my guild members rankings, but another user would see nothing as they do now). This would preserve the privacy of private reports, but also let users who use private reports be able to see an overview of of their performance and how it has changed over time.
Simply allowing the owner of a character see every ranking/estimated ranking for that character on their character profile/summary, while less desirable, would also be a great.
GitHub does something like this with the their contribution activity graph when “Public contributions only” is selected. While I personally can see all my contributions, be they to private or public repositories, visitors to my profile can only see my public contributions.