I too would like to see an addition of some of the Canadian Models (personally I would like the HRDPS or GDPS). The reason being is that these tend to do well in the Canadian Arctic due to it being linked to the ice models that the Canadians are using.
Myself and several people I know use Windy all the time. But when we go for trips to the arctic, we find the Canadian Models tend to do better up there and have to switch to another site.