I feel like there are some easy ways (albeit, it does remove some housing, but it replaces it with more) for densification in many suburbs.
There are these residential streets that are on boulevards, and they can instead feature 3-4 story buildings that are mixed use, like Avenue du-Mont-Royal. they can be also made smaller to allow more pedestrian space, then these suburbs would have their own local commercial space, instead of needing to drive to big box malls. An example is along these streets with red lines:
