I would have thought that a chinook/merlin mix would be the best bet if you wanted a " off the shelf " deal as there is already production lines , already supply chains i asumme that both could be "stepped up" for a speedier delivery schedual.
They are both combat proven , ok maybe the merlin is still to iron out the faults as its still a relitivly new platform ! and as mentioned it maybe expensive but the more you buy the cheaper it will be (wont it???)