I understand this would be impossible to fully accomplish, but what would Europe and the wider world look like if Germany and Britain had many of their post-WW2 "traits" swapped for one another?
So for instance, Britain pulls off an "Economic Miracle" after cessation of hostilities to become the largest economy in Europe. The British economy is focused primarily on high quality exports. (West) Germany goes through similar turbulence that afflicted Britain in the 1970's, and Frankfurt is a global capital of finance on par with OTL London.
Germany is the more Eurosceptic of the two and enters into the evolving European institutions at a later date. Britain is a founding member and the one that traditionally pushes for greater integration.
As much as possible, make German foreign policy more assertive, while Britain becomes less willing to intervene outside its borders. I understand that a more economically vibrant Britain is probably going to be pushed more towards interventionism, and the same factors aren't at play for either to fully reverse on this facet. Just do the best you can.
Bonus points if Germany can take Britain's role in the Special Relationship with the USA, while Britain is more focused on European affairs.