In my opinion, yes, the A220 is the best possible aircraft for AC right now.
I think they can bet on it, especially given the fact that it has been flying for quite some time now with various airlines (encountering almost no issues). We thought that it would be very difficult for AC to handle losing all of those MAX aircraft, which it certainly was at first, but they were able to adjust fairly quickly. I am sure if anything happened with the A220, it would follow the same course as the MAX did in terms of fleet constraints due to the grounding.
I would go so far as to say that AC should cancel the remaining MAX orders, and instead order more A220s. I have lost all faith in that aircraft (and even Boeing to some extent) because of how the company has behaved throughout the whole process of getting the aircraft recertified.
I am interested in seeing where others stand on this!