Nothing wrong with using Verm in place of Gibbs. No doubt that was part of the plan from the moment Verm was signed. The defence is all over the place but there is no guarantee a new face will put a stop to that. Individually the defenders at Arsenal are quality (Santos apart arguably, but then he has barely played). Arsenal fans on this very board called for Wenger to sign Mertesaker, before he was indeed signed.
The problem is the unit. They do look very uncomfortable.