Engineering for snow and wind loads is significant. The roof would have to be really stout in WNY due to the required safety factors used in the calcs. Like you said above, that has a cascading affect on superstructure, foundations, geotechnical prep, etc.
It makes a massive dent in the budget and cost analysis needs to be done.
I think a more economical stadium like Heinz Field makes more sense. Most of our AFC rivals this side of the Mississippi play outdoors. I think the Bills would be at a disadvantage on the road.