It's all lovely having an armada of foreign aircraft on standby should the worst happen. But would it not be a better use of resources to simply call in the charters if/when Monarch goes the way of the Dodo?
At worst you'll need to wait a day or so and your only expense would be extra nights in hotels, not the expense of large aircraft flying half way around the the world 'just in case'.
The ATOL protecrion scheme is a finite resource. It should be reserved and not squandered on jollies for dozens of air crews and air craft.