When this was on the table before, the thought was that there would be a "Coastal" and "Mountain" division.
I would assume Eastern would be in the Coastal with Portland State, Sac State, Davis, and Cal Poly. After that it gets dicey. I'd assume Idaho would be placed wherever Eastern goes. The last team would likely be Southern Utah to the Coastal, although NAU might be a consideration, or even Idaho State to keep with Idaho.
From a practical standpoint, one would have to assume Eastern, Montana State, and Montana would be considered the top tier and split apart. Montana and Montana State would be paired together, meaning Eastern is odd-man-out.
When this was considered before, the thought was each team would keep one rivalry alive from the other side, meaning we could still be lining up against Montana every season.
The other thing to consider would be the "rivalry" games that the conference prizes. Would we continue our artificial rivalry with Portland State? No one seems to care about that one, especially on their end. Would we take Idaho and Montana as rivals? If so, that's a tough pair of games each year... but probably the best revenue drivers we could schedule from within the league.