I am sorry to disappoint, but we don’t plan to implement this.
Switching to plain text paste means that we need to dedicate a shortcut to rich text pasting that is available only to those who have switched. This is another thing to test and potentially break if we rewrite pasting in the future. Not to mention confused support emails by users who have enabled it without knowing what it does and needing help. In other words adding the setting is easy, the hard part is maintaining it in perpetuity and dealing with user confusion.