Iry
Legend
That's certainly true, but you're running into the problem of stereotypes. The OP is concerned about the Succubus not because she has insufficient infiltration, but because (presumably) he deems the stereotypical Succubus as inappropriate for his children. Some of us think the better solution is not portraying this particular succubus as sexual.There's nothing about the situation of "evil creature replacing a noblewoman" that requires a succubus, from the little that I've heard. A smart wizard with a hat of disguise can pull off the same trick. So if the OP wants to replace it, all to the good.
It teaches a better lesson, if there is any lesson to be taught.