Stage One - a Plantagenet Empire
What the Angevin Plantagenet dynasty had not lost their lands in France, but instead continued to extend their influence and united France and the British Isles under a single Monarchy? If the Kingdom remained united, ruled by a Latin speaking elite and structured as a strict feudalist empire with slightly different customs for each kingdom, it would be one of the greatest powers in Medieval Europe. Of course, it would spend most of it's time suppressing regional revolts from Scotland and other difficult regions, and fighting Spain.
How to deal with things like the Magna Carter and Parliament? Would such ideas catch on with French Barons too? What about the war of the Roses?
Stage Two - Protestantism and Revolution (Empire Breaks Up)
I'm not sure how to deal with this part, combine the Wars of Religion and the English Civil War in one giant megaconflict lasting for the duration of the Tudor and Stuart period? The Empire could be temporally broken into a Protestant Commonweath and a Catholic Kingdom. Colonisation of America begins, conflict with Spain.
Stage Three - The Enlightenment and Reunification
The American and French Revolutionaries overthrown the Catholic Kingdom, but the Jacobins and Democrat-Republicans are weary of the puritanical and militaristic Commonwealth. Luckily for the Empire, a French general by the name of Napoleon Bonaparte defeats the Jacobins and conquers much of Europe, reunites with the Commonwealth and combines the offices of first Consul and Lord Protecter into the grand office of "Emperor of Europe". The combined naval power of England and the French Army proves nigh invincible, and America is forced into submission when Napoleon cuts off it trade supply through Louisiana and the white house is burned. The Federalists collaborate, and Napoleon is elected President of America, an office he holds only in name. The Franco-British Empire rightly considers itself the heir of the Roman Empire, and Roman law and architecture is prominent. There is freedom of religion, though the now declining Catholic faith is treated with mistrust and it is rumoured the Emperor is partial to Islam.
The Empire extends into Asia and Africa, with only Russia remaining as a counter balance to it's authority. Slavery is eventually abolished, and the Industrial Revolution changes the face of civilisation. For the Empire of Liberty, nothing could wrong. Or could it?
