Post-EDIT:
Nothing in this edit makes me more supportive of this idea. If anything, it makes me much less supportive.
Expose the child to great personalities, fictitious but realistic, inspiring, able to communicate with the child and teach them something in a context that is outside what the child perceives to be "family" or "school"....
Unfortunately parents are not enough: all children need many good quality one-to-one interactions with as many different educators as possible, and from as many different cultural backgrounds as possible
So, the point is to give the child the idea that they're hearing a number of points of view, when in reality the world around them is being manipulated as if they were playing a tabletop RPG with mommy gamemaster who maintains absolute control over every 'different' voice.
however educators, relatives and friends are usually not able or not willing to engage, cooperatively with the families, in activities so much tailored on the needs of one single child. This trivial trick would allow the child to interact with astrophysicists, musicians, artists, philosophers, mathematicians, neuroscientists, etc. - and these would not be just "mum" or "dad", they would have an aura of magic, they would be fascinating - which parents cannot usually be. And having real pen-friends is such a great educative experience for children of that age, expanding so much their normal, little microcosms.
With far less effort involved in this sort of trickery, you actually can expose your children to actual scientists, musicians and artists. (neuroscience and mathematics are... honestly... not all that fascinating for a pre-teen) This is the age of TED talks and stackexchange, youtube and the arXiv.
You are underestimating the power of a child's imagination, and substituting role-play in where none is needed.
