It was known from the very start that Achronos wasn't happy with the idea of the Webcam MVP title (after all, it wasn't earned through contribution, it was earned for winning a simple riddle/question displayed on the Webcams). Mr. Hand had to convince him of it. I can't say if the same is true of Theme Master (w/ Avatar) but I imagine that titles have been a thing of discontent with Achronos for a while.
I believe the only reason I still have my title is purely down to the Web team having more important things to worry about than removing someone's title. I've fully expected to see it disappear everytime there's some sort of title update, but so far nothing. I quite like it. Reminds me of some good times I've had on the site.
But I don't think it's worthwhile adding all those extra ones as you mentioned, for a lot of the reasons Revan mentioned, but also because I suspect that if Achronos wanted to change the current system, he would have done so already. The only thing I can speculate regarding that is that they are currently working hard on a local build of the post-Halo Bungie site. Which is going to be very interesting to see, that's for sure. I believe it's going to either totally remove the title system, leaving only titles and custom avatars for Mods/Employees, or it's going to be totally changed to better suit their next game.
Obviously it's uncertain, and we can't really speculate at this point. I would even go so far as to say that I'm not sure any amount of suggestions on our part will even remotely influence how the Web team is planning on going ahead with things, simply because we don't have the insight.
[Edited on 11.29.2011 9:28 AM PST]