I feel Boise could work if it wasn't so far away. I find that Billings and Missoula would be an interesting addition, but I think Boise is suited for AHL more than WHL which I believe happens in the far future.
I think with the rise of Americans playing the WHL will have to make a play for some of those states soon or the USHL might beat them to it. But even then I think WHL is a more exciting league due to 18 year olds not leaving for College every year.