Nico isnt going to be trusted in that position until he proves he can be, it's too vital a position to push through with players who dont get it. if the 6 isnt on it, our entire gameplan suffers badly.
Reijnders needs to be freed up for the 3rd man runs, tying him down to a midfield 2 role gives him too much defensive responsibility and removes a large portion of the threat he can offer, or if he leaves his role to offer that threat, it then leaves us wide open on transition.
He's got to be played as a second 8 that acts as a 10, putting him as an 8 with a solo 6 and another 10, again leaves us wide open.