There were two WCHA teams in the Frozen Four, and two Hockey East teams, if I remember right. It was UMD vs. Denver in one semi-final game, and Maine vs. Boston College in the other.
But you are correct, it would have been possible to seperate all the WCHA teams to have 4 of them end up in the Frozen Four. We had North Dakota, Minnesota, Minnesota-Duluth, Denver and Wisconsin all in the 16-team field.