Oliver's Unlikely Ally

Who  do you think Arrow's unlikely ally will be?  Could Thea be likely to join the team once again?  I have heard the rumor that the Huntress  is  returning, could she be the one?  Some speculated that it just might the Laurel,  but from the promo, that doesn't seem likely, or does it?

Cayden  James has a posse, and he will stop at nothing.  What does  he do to the students  on the school bus? William and his classmates are threatened, so that will affect Oliver  deeply.  Since, in the  written information on the promo, they say he turns to an unlikely ally, it would seem to me that it would not be someone we usually think of as someone likely to  work with Oliver.  Perhaps a villain from the past, like the Huntress, but would she be enough? 

Who  will Oliver turn to?  Can't wait until Thursday!