Can non Shinigami use a form of magic... what if a human figured out magic or learned it to tap into their spiritual powers! Orohime gained some training in Kido, so why not?

Here is an oc idea for that...

A boy ( or girl really, doesn't really matter) is attacked by a hallow at a young age and studies all they can to find a way to fight back. They eventually learn about magic, from various cultures, and they practice until they manage to tap into their spiritual powers and manage to cast spells.

It would be the opposite of Ichigo, who was born to tremendous power and only uses his Sword and hand to hand skills... I can see them learning some extra things and focusing on healing to help fight Hallows...

Really it would be a fun way to play with power and expand on spiritual power.