I could be mistaken but unless you plan to substantially under inflate the tires, which obviously is not recommended, I don't think you're going to see as much improvement in the ride softness as you think.
In my experience since I've owned these vehicles, is that the relationship between ride softness and tire size isn't a linear one. Meaning that (assuming one keeps the same overall diameter) the amount of increased stiffness observed when going from let's say 17" to 20" wheels is much less than when stepping up to 22s. For example, I noticed almost no ride difference going from the oem 18" setup of the hybrid to the 20" setup of the Denali. A very slight increase in stiffness when going to the 22" oem wheels, and a huge difference going to 24" with 295/35/24 tires.
So the graph is more a curve, with the 16/17/18/20 inch wheels at the flatter part of the curve, then as you go bigger the curve steepens ... if that makes sense?
No doubt a small improvement will be achieved in ride softness, but probably not enough to justify the compromises, be they esthetic or handling related. 2 cents.
