When the UK controls territories uninterrupted west of West India, UK may choose every turn to transfer those IPCs (Persia, Iraq, Transjordan) to UK Pacific if it so wishes, giving UK a little flexibility.
I’ve been thinking of letting UK pick a new capital (Ottawa, South Africa) if London is lost, but suspect it might upset the balance a bit. If you use Larry Harris’ latest Alpha, you could implement this instead of bringing the USA in the war.
Or alternatively, make a British Empire out of 5 factions (Canada, UK, South Africa, India and ANZAC), and let UK transfer cash between the groups with limitations. Group Canada-UK-Africa together and also Asia-Pacific-Australia with Middle East assigned to either side. Could also be imposed limits such as Canada 7 IPC, South Africa 7 IPC to prevent enormous disbalance.