I have, in the anime Konosuba. Except in that universe, the succubus don’t sleep with their marks. Instead you hire a succubus at an establishment. They would then appear at your side while you sleep and give you the erotic dream you asked for on the form you filled out. Here’s a few pics. Except the poor thing got caught by the MC’s idiotic trio of female party members while on her way to the MC’s room. The useless Goddess, the explosion happy fire mage and the masochistic crusader.
Um, just because a female is petite, doesn’t mean she has the “body of a child”. It just means she has a small or short frame. She can still be developed in various areas and not look anything like a child. I know various petite women in real life and believe me, they would probably drop kick you for calling them a child.
I’d say leave her the way she is. Just because someone is “unsettled” by her appearance, doesn’t mean you have to change her appearance because someone can’t deal with it. If they are SO unsettled by it, they can choose not to romance her, simple as that.
For me I’d each do a play through for Sophia, Emilia and Tara. I’d probably go for Emilia first, since a shy succubus sounds adorable, that or Tara.