I thought Propper was one of our better players last season. Suspect reason he plays a more withdrawn role is that Groß plays ahead of him and we lack pace all over the park so players are deeper as a result.
That's an issue all round. Trossard can play no 10. Propper does for Holland. Gross is the man in possession. Andone wouldn't be out of place there.
Of those only Propper CAN play centre mid / holding. Gross was hopeless at it IMO. The question is, does Propper want to? The other question is, what to do with the others?