So if we were to guess at likely comic counterparts to Skye, knowing what we know now?
Mantis - pre GoG, pre cosmic, pre green, original flavor Mantis from the Avengers. Half Vietnamese orphan with cosmic destiny. Ties to Zodiac.
Carmella Black Scorpion - secret daughter of AIM Scientist Supreme Monica Rapaccinni, this one matches up to sky in a lot of ways, and could have some interesting possibilities. She is a sub D list Marvel character who has only appeared a handful of times. She is of Asian extraction (Madripoor in the comic universe), she was a secret AIM experiment given over to adoption, only late discovering that her mother was the leader of AIM. She is a low level super powered SHIELD special operative, and her father is George Tarleton, later evolved into MODOK.
Nico Minoru, Runaways - unlikely. Magic using Japanese goth chick, daughter of super villains. Doesn't fit in well to AoS and Marvel has been talking up a Runaways project for ages. She would be crucial to that.
Jessica Drew, Spider Woman - unlikely. Too associated with Avengers these days. Too associated with tight spandex. Too convoluted of a backstory. If we see her it will be as an Avenger.
Zuzha Yu, Puck 2, Alpha Flight - half Chinese super powered daughter of the Marvel character Peter Dinklage should have been tapped to play, Alpha Flights Puck. Honestly a virtually unknown fairly un memorable character. Even the most die hard Marvel Zombies would be scratching their heads over this one. Unlikely that the writers of AiS have even heard of this character.
My 2c for leading contender. Carmilla Black, Scorpion. SHIELD Civilian special agent. AIM, MODOK, right age. If Skye is any existing ?Marvel character I would bet this one.
As far as a new character? Maybe Asgardian or more likely Vanaheim (Hogun's people from Thor movies)?