In the game we currently have a fairly robust plethora of options for our character's titles (be they pre or post affixed) but there are always more that could be thought of or borrowed from other lore characters that would fit really well with your characters image.
Being that the format won't be followed, I'm not gonna bother setting one up. Can you think of any missing titles you'd like to see obtainable and if you feel like it perhaps explain why and possibly how you'd like them to be earned.
Just to start off, I feel there really should have been better titles for earning the highest achievements in Proving Grounds. Maybe they could be made even more complex and class-universal and at wave 50 you'd earn special titles for your role. For DPS, "the Unrelenting." For Tank, "The Unbreakable." And one I've had in mind for quite a while, for healers "Life-Binder."