I like the way you think on this.
In all honesty it's unlikely a team leaves but would be nice to have happen. I definitely would not add another team. The way I look at it is I would much rather have a couple of more games versus BU, BC, UNH, Northeastern, and Providence versus a couple games against Holy Cross or Sacred Heart. UVM has been in the league close to 20 years now and I still can't get very excited about playing them.
Well, we did see Northern Indiana Community College leave the league a few years ago.
League members (almost?) never get kicked out, the ones who leave either do so of their own volition, or with a few others to join another league OR start their own new league with others. It's how Hockey East started 35+ years ago. HEA has already set the precedent of going up to 12 teams for a few years with NICC. Frankly, I was happy when it was a 10 team league too. But unless someone else drops, that's not gonna happen. And I don't see anyone dropping or changing leagues from the current league membership. It's WAY more likely we'll see HEA going back to 12 teams at some point. Then the question is, who is the #12 team, and (perhaps most importantly) why? NICC was always a good "who", not such a good "why" for HEA.
In their wettest of wet dreams, I'm sure HEA would love to have #12 be a New York metro team, but there have never been any obvious candidates there. Nor does it seem likely it would happen anytime in the foreseeable future either. So assuming HEA remains a New England proposition, you look around at ECAC or AHA programs that are away from saturated HEA markets, and it kind of leads you to Southern CT, especially now that UConn is (sadly) in the mix. Holy Cross arguably also works since HEA does have a void in between the Boston and Springfield markets, and (last time I checked) Worcester was still the second biggest city in New England. And HC is already a member of the women's HEA, so most likely it's HC.
IF HEA does go back to 12 teams, they can still hit the old 27 league games target if they split it into two divisions, play 3 games per season against 5 divisional rivals (15) and 2 games/season against 6 non-division members (12). But one can only imagine the free-for-all that would break out when figuring out which programs went to which divisions. All out war, dissatisfied members, and (probably in less than 5 years) another break-out league to carve HEA in half (or close).
So there are no easy answers. Unless of course UConn just left, and Commish PR pulled up the drawbridge afterwards to close up the castle. Letting them join in the first place was what unbalanced things to begin with, whose dumb idea was that?!?