They actually don't have a lot of options for a partial swap.
Verratti (never happening)
Di Maria (same)
Rabiot (eventually leaving, would be a brilliant addition but will go to a bigger club)
Draxler (imagine squeezing him into same midfield as Gomes and Sigurdsson; no defending would happen)
Lassana Diarra (old and probably not good either)
Antoine Bernende (19 year old with two first team appearances; we have more experienced youngsters on the books already)
I now understand their interest in Gana. They have about three players of the requisite quality for what they want to accomplish, one of whom appears to have been frozen out (Rabiot), and none are particularly strong defensively.
Meunier would be the best shout for someone we could use but he's already 27 and fullbacks age rapidly.