I wouldn't worry so much about possible party ramifications right now... there's still plenty of time for everyone to figure out what kind of impact this might have... Jango especially. And like stonegod says... Jango can either fully embrace what has happened, or try to fight it. Doesn't matter to me which way he goes. The roleplaying experiences will result regardless, and what the other characters do when the group comes back together we can worry about when it happens. (Although I would like to point out that the "new skin" is barely imperceptible at Level 1, and it's only over subsequent levels that things become more obvious. At by that point, Jango should know whether he wants to try and have it removed, or to try and cover it with clothing or even illusions. He
IS a sorcerer, don't forget.
A little polymorph works wonders.)
As far as any other prestige classes for other folks or whatever... I don't think you guys need to worry about powergaming problems. Truth be told, on the last module you guys did an exceedingly good job at AVOIDING combat by using smart tactics, silent surprises, and negotiation... and if that kind of thing continues, it won't make a difference if your characters are kitted out for combat to the best degree or not. So make your choices based on how what your characters "wants" are. What do they want? What are their goals?
As I've been trying to make clear this entire time... I'm all about the roleplaying of the character. You make choices with what your character believes / tries to do... you'll be rewarded for it (or cursed for it, depending on your take of the situation.) Velmont has made some very broad character choices, and what has happened is a direct result of that. Brogarn sending Skarghash to see the Daggerspell Guardians is a character choice that might result in some interesting things. Khalia can get more involved in Flame heirarchy, especially on this crusade. Ari can become a full-fledged member of Deneith again. All of these choices are up to you, and we'll see how things happen. But you need to make a choice.