AC already has a B767 with 260 seats in it's fleet...a pineapple with a 18J/242Y config.
The article isn't quite correct with the math on # of seats. AC's densest XM'd B767 has 211 seats - not the 225 stated in the article. Add 50 seats and you get a pineapple.
Even though they are rumoured to be going to 3-4-3 B777s, they don't need to go 2-4-2 with the LCC to get the density they want.