I found an old “All Races, All Classes” hack on another forum. Actually, I found it on a number of different forums, seemingly swapping hands and changing a little each time. However, the last update I could find to it seemed to be around 2013, and predictably when I tried to apply it (after backing up my database because I was definitely leery of applying it) there were definitely a bunch of things that were broken, columns that needed to be renamed, etc.
I seem to have, after some tweaking, gotten it working, but I wanted someone who’s more familiar with the format of the current world database to look over it and maybe see if they could create a better updated version. I’ve got some problems with the current version. Noticably, Undead Hunters do not seem to properly start with the Guns skill. I tried to modify playercreateinfo_skills to make this work, and while I was able to give them the “Bows” skill successfully (and then modify playercreateinfo_item so they started with a bow) I wasn’t able to give them “Guns”. I haven’t done super extensive testing so I don’t know what other issues might be there, which is why I wanted someone with more familiarity to give it a look before I went any further.
The “world.sql” file is the original patch I found (I’d give credit but frankly nobody seems to know who originally wrote this), the “worldnew.sql” file is the edits I’ve made so far. Notably, I clipped out the entire playercreatinfo_spell table that it added because it seemed to just cause problems without actually fixing anythnig, really.
On another note, I’d actually be interested to see if someone could create a version of this that could enable just those race/class combinations that became available in Cataclysm (Undead Hunters, Tauren Paladins, Tauren Priests, Dwarven Shamans, Dwarven Mages, Troll Druids, Human Hunters, Night Elf Mages, Orc Mages, Gnome Priests) instead of enabling literally every race to play literally every class. I’m sure it’d be simple enough but I’m not anywhere near knowledgable enough in editing the world database to do this.
There was also an MPQ that came with this patch to enable selecting these classes/races clientside but I don’t think it’s necessary in order to fix the issues with the current one. I imagine I might need to make a new one (DBC editing, I’m betting?) if I were to make it just the Cataclysm combos though.