The way I see it, if we're doing away with the concept of "Darth" being a Sith title, it shouldn't be a personalized Sith title, either. I understand and agree with you wanting to show how the Jedi and Sith are two sides of the same coin, but this is one area where I think a direct parallel isn't necessary. In fact, it's a reversal of how things go in Lucas' universe in which the Jedi go through no name changes as they work their way through the ranks, but all Sith are dubbed "Darth ____" when joining the order.