A lot of places hint that Maggie is a cross between Bart and Lisa in the future. "She's a hellion but she has an angelic voice"

Maggie has learned both off Bart and Lisa I probably think she may have elements of homer and marge too. I can imagine her as a Lazy teenager but with Marges heart.

When older, Maggie will probably be a well rounded person up for a laugh but repectful and kind at the same time. The flashforwards are only a theoretical future of what could happen as the Simpsons havent actually set an episode in the future yet (to my knowledge) they are all imaginations, dreams and fortune telling.

Has this been discussed before as may be an interesting topic. What influences will shape maggie and how?

Most characters on the show are left handed. This has nothing to do with the fact that Bart's left handed and where Maggie gets her traits.

The simple fact is that Matt Groening himself is left handed and that results in the characters gaining it off him.

Besides, if I remember right there have been situations where Maggie has used her right hand. Such has playing the Xylophone in A Streetcar Named Marge. So in that case, you can say that Maggie is ambidextrous in that she could potentially write with both hands.

Maggie is the most flexible character in that nothing about her is permanently fixed. Take her overbite when the pacifier is out of her mouth for example.