any delay around the route for whatever reason has knock on effect that forces a 24hr delay
That's not really true - a major reason that the airbridge takes the form that it does is to allow for slight delays without having to delay 24hrs. Of course, there's always a point where a crew will run out of CDT but we try to make that as far away as possible. Sadly though, whenever tasks are planned close to a max Crew Duty Day, it means that there is little or no fat for delays, and that happens all too regularly.