I have an English dance that has a similar sequence, with one half star, then a full star with new neighbors and another full star back with original neighbors. As Chris suggests, I find that part a bit trickier to teach than I expected. The difficulty is in the orientation (particularly on the ends), not the timing. I set the dance to a half-length version of Larry Unger's Two Rivers which is in waltz time, so the timing could be different in contra. I think the hands-across style star used in most English dances facilitates that kind of transition. I think it creates the nice flow pattern you envision, looking forward to trying it. Nice idea, Luke!