I've played this game and to be honest, I really wish we could pick our own path... those of us who wish for our characters to be evil.... will start out like normal but will get a letter from Malistaire Drake Inviting us to Join him... There will be two options Join him and become evil... Or Refuse and stay good. You will be fighting Good Wizard NPCs while Players who have sided with evil will be able to join you... There will be a whole load of quests Given to you by either Malistaire or his Forces... eventually there will be the final between Malistaire and the evil players vs the Players who refused to be evil... after Malistaire is defeated for the first time... the evil players will be teleported away... and get a litter from Headmaster amborse stating how dissapointed he is in the player and how he/she had so much potential. and how the evil Player is no longer welcome in Wizard City. then the evil players will get another letter from Malistaire the undying stating that he is still Alive and wants his followers(including the evil players) to seek him out for the second finally battle... after the defeat of the defeat of Malistaire the Undying. The good player will get the default letter from Moranthe while the evil players will get a new different letter from her... the letter from Moranthe for the evil Character will state how she knows that you were allied with Malistaire and she wishes to complete his goal... The evil players will be stuck with accepting to join her... Morganthe, and her minions will give the player all sorts of quest... for the evil players. eventually the final battle between Morganthe and the Evil players vs the Good Players.... After her defeat The Evil Players will gain a new letter from Morganthe that was left for them. the letter will tell the evil players to avenge her and and Malistaire... that will give the evil players many more quests... eventually the evil players will have to fight headmaster Ambrose and the good players.... this update will come with new Achievements reserved for the evil players... and after defeating the headmaster they will get a new Achievement/Title called Tyrant of Wizard City instead of hero of Wizard city... you will then be able to continue fighting the good players and good Npcs all around the Spiral...
That is just a whole realm of PvP. But not every one would want to play that. I know I wouldn't and I would end my subs (3) very quickly. The only place, Players should be able to fight other players is in the PvP Arena.
Honestly as cool as the dark side would be, it's not feasible. Rewriting the content of the current game for evil players would be at least as large of an undertaking as writing a full arc, and then each world has the work multiplied since you have to create story for both good and evil.