This reminds me of another feature idea which was a customizable conclusion to letters that would be automatically placed at the end. For example: "For the Kingdom," in place of a "sincerely,". Though I don't remember if it was ever officially requested/rejected, I do remember one of the arguments against it was the less personalized feel. Essentially it creates/incentivizes a boiler plate which feels lifeless.
I suspect this idea would share a similar concern. I'm assuming this is what you had in mind when you added the "downside" of blandness.
