4 years ago that would be a good signing but now a centre back who cant get into the Chelsea side is not the answer. But getting a top CB on loan seems very unlikely. It still seems insane that we aren't going to give Ramsey a contract regardless of money as he surely deserves the same as Mikhi or 66% of Ozil's salary as he has done more for Arsenal than those really.
Sell Ozil even if its a nominal fee to get the salary off the payroll. Sell Mustafi.