I could work
How a bout the UK not rushing to grant independence to almost every country we controlled but a more targeted one i.e get shot of the ones that have zero strategic value keep the rest as Dominions but on a tight leach.Use the money from the sale of natural resources to boast all of the dominions up to first world levels and have a fully integrated army navy and Air Force.
Invest heavily in renewables in each country to make them ready or the time oil runs out also keep a few oil and gas fields in the back pocket just in case.
All country's to have a Westminster style government.
The big change would be the creation of a strong imperial parlement that moves location every say 8 years and limit the amount of hangers on that move to the bare minimum most support staff to come from the new home of the parliament a big win and saves a few bob.
Having a standard armed forces would enable a highly trained and affective force.
We would not only be an energy super power but also a military one.