Eastern Washington won the FCS title a couple of seasons ago I think. Those teams often could compete or beat most of the WAC type teams. It says something when there are FCS teams still out there like Montana that turned down a WAC invitation.
Montana and Montana state are happy where they are. Neither are hurting for money, and both outdraw Vanderbilt. But mostly there is no way either could compete in fbs
Sort of, a circular rivalry of sorts has always existed between Wazzu, Idaho, Boise State, Idaho State, Montana and Montana State. All of them have been major division and in the same conference at some point or another going back like fifty years or so.