Liam:
Surely easier to keep the pattern the same and use the Aussies and Canadians in whatever order is necessary
Sorry Liam, but what makes you think they can continue to violate the CoS of Aussies and Canadians? They were excluded from the offer to OPT IN, because the company is not allowed to approach individuals with changes to their CoS. That would be considered a breach of collective bargaining / enterprise agreement. They are NOT excluded from ceasing to violate their CoS.
If anything, the FDPs of Canadians at least will be more limiting since they will be un-aclimatised. If they achieve the less restrictive rest, then they can go to 11.5 FDP, which is way too short for this pattern. Considering that most of our overnights fit into the 18-30 hr rest block that they are supposed to avoid, it is likely that their max FDP will actually be 10.5 hrs.