I feel like AC could fill a 779 or A351 even in the winter with a flight to Mexico. I believe they already fly the high density 77W as it is now. Not sure what the numbers are for that flight but given that they do it year after year it must be decent.

It would be nice if they offered more premium seats but I doubt they will give that they might use these planes for short-med hauls and are likely more focused on number of seats.

They would definitely get they're use out either option year round.