There is a trend amongst City fans to assume that a deep lying midfielder has to be a hard tackling De Jong like player or a player with an engine like Fern or Milner but it could be a technical player like De Bruyne. Guardiola played in that position. Players like Alonso and Javi Martinez played a deep midfield role for Bayern so I could see De Bruyne playing there.
I prefer him using his running power and passing in danger areas but when you have players like B.Silva, David Silva etc in advanced positions, it might make sense to use him in a deeper role.