Suppose that the UK recognized that the surest way to preserve the empire was to fully integrate it? So in the 1870s, they begin the process of federalization. In addition to political integration, the native populations are also taught English and the British way of life, and are given modern infrastructure.
You can have any number of PODs to make this happen. I personally think that the PM with the greatest chance of doing this was Gladstone. In any event, what happens?