I am new to this forum but as I was reading the books again one thing came to my mind and I had no one around me to discuss it.
The Valonqar may be Little Finger!
He is a little brother, literally and in many other ways he is "little". He conspires to kill Joeffry and is obviously very ambitious and wants to sit the Iron Throne. Cersei and her children are the most important people in his way, now that Tywin and his brother are dead and Varys is gone. He is able to conspire to kill Tommen and Myrcella too when he sees an opportunity for himself. Also he is the only one cunning and cruel enough to be able to strangle Cersei with his own hands.
It would be so interesting if Sansa becomes the queen that overthrows Cersei and all the characters who most consider heros of the saga, Danny, Jon (if not dead yet), Arya and Tyrion would unite to fight her!
I love how many possibilities these books have.