Little update:
I managed to look into this for you. Thing is, you CAN change them. Actually, it's quite easy.
Each class is 0x63 (or 99) bytes in size.
The very first byte determines if the class is active or not. Set it to 0 and the default class is used. Set it to 1 and the information following is used.

class DefaultClass
      byte DefaultActive;
      char _0x0002[0x0062];

class DefaultClasses
     DefaultClass Class1;
     DefaultClass Class2;
     DefaultClass Class3;
     DefaultClass Class4;
     char unk1[99];
     DefaultClass Class5;
     DefaultClass Class6;
     DefaultClass Class7;
     DefaultClass Class8;
     DefaultClass Class9;
     DefaultClass Class10;
Or something like that. I was using ReClass just now on it....But then I knocked my laptop and fked up the hard disk so I lost it....