So major revamps of a character, like a change of class/race/gender...
What is allowed and what is not and how does it work? Reapply the characterprofile with the changes both minor and revamps of RP mentioned or are minor things just done with a note to the GMs?
I would say make it an entirely new character. You can take the old profile, and have it moved to deceased, or MIA, then delete the physical character and make a new one. That's what I'd do, at least.
I had a character named Marie who was a human, but deleted and made a gnome in place. I just act like it's an entirely different character, because it's quite likely at least two people in Azeroth would share the first name.
Not sure what the rules are, but Race/Gender I totally agree, make an entirely new character. Class...? Well, depends what you're changing. I don't see why you shouldn't (with much work) be able to make class changes in reasonable situations. Such as if a Paladin strays from the Light (becoming a Warrior, Hunter, or Rogue) or maybe if a Warlock cuts it off with the demons he should be able to become a Mage again.
Just my two copper.
With the restart I rerolled my draenei anchorite as a paladin OOCly to offer more goodlooking RP gear. The big problem now is that I cannot use staffs as paladin after the restart AND the weapons aquired by the commands cannot be used to use all the flashy spells. So now I am starting to have second and third thoughts about the classchange.