Can Kumagami in Charlotte possess Yuu Otosaka?
Yes, seeing that Yusa's power is Spiritism, she can be a medium for the dead. Which is also mentioned in the wikia. 


  Yusa has the ability of Spiritism. She is understood to be a medium,
  seemingly capable of channeling and/or conversing with the dead.


So it is not entirely impossible so long as they have a way to communicate with Kumogami's soul.