I don't know, it is an interesting thing she has been absent from the games, maybe it is to give Link this kind of 'special' status, then again, he has had a sister which kind of take away the only kid and therefore special, hahahah.
I dunno, it would be odd, just like having the sister was odd when first announced but it could be pulled up nicely. After all if Link could leave grandma, he can leave mum too if required to full fill his destiny. Maybe it will make it awkward if link decides not to return in the end when it is her mother the one waiting instead.
i think it would be cool to have a mom like instead of a granma who is so protective of link haveing a sword and so not welling to give him a sheld when he the the hero of hyrule i mean they should be a mother how could arial be born with out a mother i dont think the granma made her so it would me most likely they should be mom