As far as I know, and remembering all the MMORPG games I've played in the past years, there's no game so far that has implemented custom titles aside from obtainable in-game titles (if that's the case)
WHY? is there a reason this feature isn't made available in any game, yet many players dream of it?
And yet a much profound question is, why haven't private servers done this either? In Warmane's case, you do implement a transmogrify system in an expansion where it was not available. And this is not "Blizzlike" at all and has nothing to do with Blizzard. It is obviously a custom mod for a custom realm where PVE bosses are boosted unline Icecrow, etc
If you're not going to adhere to real Blizzlike behaviour, why not implement an extra feature that might as well attract a fair number of players?
I don't see how having thousands of players running around at the same time with the titles they came up with would be beneficial in any possible way.
I imagine there'd be lots of stupid, pointless, and overall, just bad titles. I don't like that idea, not at all, but then again, to each their own. :)
However, I could imagine a situation in which after winning a certain event made by Warmane staff the player who won would be able to pick a title that is decent, or created for him as a winner of the event.