I think our strongest assets are Laca and Auba and we need to play both, which to my mind is best done through a 4-3-1-2 formation. Given that, my transfer window strawman is the following:
Out: Cech, Lichtsteiner, Jenks (2M), Chambers (20M), Mustafi (20M), Elneny (5M), Xhaka (30M), Ozil (25M), Mkhi (20M)
In: Mancini (25M), Malang Sarr (15M), Aarons (15M), Doucoure (35M), Herrera (Free), Pellegrini (30M), Under (50M)
That's admittedly a stretch, but can be done and will fill us well in most positions except 2nd GK and 4th choice striker (don't think Nketiah is good enough yet).