How to keep the British Empire together all the way to the present, with Britain remaining the global superpower as opposed to America? Preferably with European and Asian Constitutional Monarchies (Germany, Russia, Italy, Japan, Siam, etc.) still tagging after the British instead of pandering to Washington and its liberal democratic policies (which according to many people on this site isn't actually as good as the Americans proclaim it to be).
Well, to have the slightest chance to achieve it, you would need the british empire to cease being the empire of Britain and to become much more similar to the roman empire. Which means really integrating a large and significant part of the population of the various territories of the empire, especially the ruling elite but not only them. It means accepting that Britain becomes what it is - a minority inside the empire - and that it loses control and that a political faction coming from this colony or this other colony becomes dominant because it weighs more in terms of power and resources or is located on the strategic point of the age.
That's what the roman empire did with its italian-spaniard emperors in the 2nd century, with its italian-african emperors in the first half of the 3rd century (both Antonines and Severi partly descended from italian settlers in Spain and Africa), with its illyrian emperors from the late 3rd century to the late 4th century.
I definitly can't buy the idea that India could be part of such an empire because India's weight was far far too important. You can't found a new nation that is different from the part that weighs 75 or 80% of the total population and which has such a strong and distinct cultural identity.
And I think it's the same for the african colonies.
Last, you have to deal with the paradox of communications and identity.
To hold together such an empire you need fast and intense communications that did not exist before the late 20th century. Without fast and intense communications and transports, there is a somewhat irresistible trend to set local independant powers in several distant territories.
And if you want to forge a common identity by melting former different identities into a common new one, you need to force it more or less violently on people and you need this people to enjoy only weak communications means so that they have no alternative and are forced to adapt.
Consider the fact that the emergence of nations in the 19th century and early 20th century was largely correlated to the modernization of the printing press (with the various rotary systems that enabled to spread cultural works, language, ...etc) that strengthened local identities or enabled to forge a nation on ancient common cultural characteristics.
And that before this there was religion. Religions were and still largely are a very strong part of national identities. When those religions are too different, it's hard to forge a common nation.