A debate begins!
I don't see the need for a spare in this case. Revert to 737 or use one of the KC30s if required or hire a jet or use RPT if the govt one doesn't work or is needed for something else.
For the emergency case there is always the case of places and things the charter world can't/won't/not available in time frame or won't be 'cleared' to do.
Bali bombing springs to mind here.
Also I would have this one rigged for medivac work if feasible but C17 probably has this covered now.
I agree funding with the GFC/government debt situation would make it difficult and unlikely but I was saying that about money for the Battlefield lifter too but that seems to be underway ...... but still, believe it when I see it.