Khedira would be a great signing for any club in the prem. Even City in my view. Disagree with people saying he's been average and 2 terrible seasons, he was pretty decent when he played, Madrid just had too many CM's and he got a few injuries.
For me if Arsenal signed him they would have signed the two players they've been crying out for for years, a top quality CM who positionally is excellent, breaks up play with experience and know how. And a winger / forward who offers a bit defensively pressing, and going forward adds a new dimension to their play.
If they sign a good striker different to Giroud they would have had a brilliant summer. Obviously cover for Sagna too required now.