This may be a naive question, but surely EK will eventually reach the point where it is more cost-effective to allow crews to be based in their home countries? With multiple daily flights to/from London, US points, Australia, etc from where many Emirates crews are expatriate Dubai residents, it surely would be efficient to operate those services using crews based at the other end of the route. The saving from not having to fund residential, education and transport costs would surely outweigh any inefficiency arising from having a number of smaller bases worldwide than one central base?
You could also build a marathon crew hotel at DXB to host crews whilst down-route there instead of paying a small fortune for overseas crew hotac.