Part of the problem in this sort of scenario is that airport ops managers (sitting in cosy offices) risk asses everything to death and are driven by the accountants. Making their airfield available for diversions depends on things like stands and handling availability or simply whether there is enough profit to be made for the extra hassle. At the other end of the line, a Commander through company policy and unexpected changing circumstances can end up only a few minutes away for having to adapt from following the rules to doing what is necessary to save life.
I had a classic example of this once when three jets arrived in the hold at ABZ when the weather had fallen below limits and it was not forecast. Simultaneously, the controller put out a broadcast announcing that neither EDI, GLA or INV were accepting diversions. We all had plenty fuel but ended up having a bizarre RT conversation about exactly what did they want us to do then and when would it be convenient for these airports for us to say the "M" word. The controller quickly picked up on the point we were making and strangely, the three airports suddenly started taking diversions. This does highlight the disconnect in safety management between airline minimum fuel policies and the way ATC and Airfield ops think. The Drone incident at LGW and the Multiple pan / Maydays a couple of years ago when there was smoke in the atmosphere quickly start to show how easily things can start to break down when things go wrong on a large scale.