There's too much focus on the front two -for instance, whether Austin can play in such a system but that misses the real problem IMO.
Crucial to a diamond are the two outside central midfielders - the so-called 'shuttlers' in the system. Presumably that's Clasie and JWP who'll play in front of Romeu at the base of the diamond.
The amount of running required for the position is substantial -not only to fan wide from inside and provide width but also to protect the fullbacks. In effect, they have to be pure athletes. That's what allows the front men to occupy more central positions where they can be most dangerous.
And yet I can't think of any two players in our squad who least merit the description 'athletic' than JWP and Clasie, whatever other qualities they might bring. If they can't provide the energy and mobility, it puts pressure on the runs and positions that the front two can take up.