Generally, when we are talking about crew shortages, we are talking about situations that the airlines could have known well in advance, like not having adequate training for crews probably months in advance.
I would support arrangements for special exemptions for airlines that operate north of a certain geographical point in very scarcely populated areas and territories. That, however, should not apply to an airline operating out of, say, Sydney, Nova Scotia, or Halifax, Nova Scotia, or similarly well-populated areas.
The assumption of any passenger protection regulation should be that the airline is responsible for the business decision that it makes, and that has to include adequate contingencies.