Good post but Sergio is open to the right hand so I'd give GGG a shot.
For me, Proska is made for Golovkin and he'll get battered. So I'd like to see, in this order of preferability;
GGG Vs Pirog
GGG Vs Quillin/HNDNJ winner
GGG Vs Sturm/Geale winner
Any of those would be great, the best fighting the best might well elevate the current 160lb division from one with great potential to a competitive division of real quality.