rollin:
One thing to realize about a "letters" contest is that it forces you to write in 1st person POV. Some have expressed discomfort with the use this POV, so perhaps that should be taken into account.
If you're a monarch you can use first person plural: "We are most amused...", or a fraction lower, "one is amused...". It would also be possible for other parties to join in the correspondence: "My client has informed me that..."; "My daughter has told me that...".
I like the idea with the twists added.