I've got it working on 2.30 on another forums that I'm an admin on (
http://www.wc3campaigns.com ).
I think I had to slightly modify some parts of the code, but I forget what.
My site's forums are 2.29 because all the hacks I was writing and the majority of the hacks available are 2.2x.
As per dissallowing users to select their class, I'm afraid that isn't possible at the moment, since i never found it necessary to add the current title Class of a user into the user edit section of the Admin CP. It's an end-user option, one that you already have enough control over.
The next version I release WILL have the Title Class option available in the User modify section of the Admin CP, as well as having the ability to set permissions to the title classes per user group (not sure yet how i'm setting those permissions... but I'll figure it out).
The next version will also immediately update a User's Title upon selecting it in the User CP.
And yes, this hack does affect the registration pages. (I was pretty thorough on it.... wasn't going to have it available in the user profile but not the register profile)