So would you just have Canada be a separate power, but they can choose to “give” their IPCs to London? If London falls they collect for territories in North America (and Brazil?) but can only mobilize in Quebec?
No Canada is completely a separate power - IPCs are not shared with London and if London falls, it means nothing for the Canadians (except they better load up on Vaseline)…LOL.
London’s IPCs are tied to only those in the west that it directly controls down to Rhodesia. South Africa is a 3 IPC Minor Ally in my game (IPCs are separate and production is separate - all gains go towards the UK however - SA is ALWAYS 3 IPCs).
Of course, SEAC (India, etc) is also completely separate.
The only thing that is tied together among all Commonwealth nations is that they MAY move together in unison (provided those same units were not moved on the same turn already). In other words, Canadian troops may board, and be moved by UK transports as long as they’ve not moved already on their own, and vice versa.
It’s pretty clean and it works well, AND I think it’s historically accurate (units of all the Commonwealth typically did work together - Canadians under UK & US command at Normandy, Australian-Royal navy joint task forces, etc).