I see it like this.
Half back flank on the right opponent : yes
Midfield : stop with the jokes please
Forward : see midfield
Playing him in any other position that on the 3rd or 4th tall forward is not going to work. He cant kick very well and is slow for his size. He plays well and someone of similar size who is not that quick. But he can adjust to that if he is not drragged back to full back. He will give us an edge with his reading of the play, his very good spoiling and his desire to help out other defenders.
In short he will get goals kicked on him on the half back line but also save goals and provide a steady defensive influence down there.
He is not the future in my opinion but I am happy for him to get games as long as it is on the half back line. Edwards, Flint are not ready. Russell is just about and he can take the really quick med/small forward. Teague can take the mid sized (185 to 190) forward. AW can move out to the wing.
Trying to turn Teague into a "defensive forward" or one of the rotations in the midfield is just going to end up ruining his fragile confidence. Let him succeed or fail where he plays his best football.