Actually, I like the concept of separating the British Empire in 2-3 parts (The United Kingdom with its two economies & and the independent Nation ANZAC).
A further separation by making Canada a 3rd part of the UK economy or a separate Nation like ANZAC seams interesting on the first look, but
a) this would weaken the UK-European economy very much and
b) its income of 7(?) IPCs is too low to be useful in any way.
What came to my mind before I opened this topic was enabling the UK-player to Redirect a fixed contingent 5, 10 or 15 IPCs from one economy to the other during the collect income phase. (Like in ColumbiaGames “EuroFront”) For each group of 5 redirected IPCs one 1d6 is rolled and the result is the amount of IPCs that arrives on the other side of the world (Treat all rolled “6” as a “5”).
I’m not quite certain if this would give the allies too much flexibility.