The turning undine thing would be a great skill to have for a healer (the fighters can generally manage on their own) possably as a new skill in the new healer tests (that are due in on the 12 of never)
Although I do see the possibility of it
a)putting the healers at risk as they try to kill the undine and
b) taking healing away from the fighters and mystics of a group

Bob
that sounds like a great storyline, completely impossible but very imaginative.
Unfortunately even lyfed exiles cant attack in TC (maybe you could move it to the badlands, have it seem like an accident in a game of CTF).
And although ive never seen it happen (i doubt if anybody has) using the luminescent culture to lyfe yourself would bring up a blue box like the salve does spoiling the illusion.
All this would achieve would be a banning on lyfes in the badlands and even then there is nothing the exiles could do to keep them out.