But, how many D1 Hockey programs that asked for an affiliation with B1G hockey were 1) AAU, 2) contiguous (possible bigger concerns with hockey due to travel schedules), and 3) would have an instant impact? The only non-AAU program I can see is ND and a) there is a lot of bad history between the two and b) there appears to be conflicting stories as to who asked who first, resulting in c) my belief that the B1G wants ND ‘all or nothing.’ Looking at the AAU list in light of B1G allowing an affiliation with Johns Hopkins in lacrosse, makes Boston U stand out.
While non-AAU, both Denver and North Dakota are major programs that expressed some interest - and North Dakota is technically contiguous (although admittedly in the wrong direction). ND expressed interest as well but as you mentioned there's very little motivation for the Big Ten to let them pick and choose their alliances.
BU would've checked all those boxes but as someone else mentioned Hockey East is pretty stable and I don't think Big Ten felt that they needed another star when they already had 4 of the best teams in college hockey in its new league. The Big Ten was already indirectly responsible for 2 hockey leagues collapsing when the Big Ten Hockey league was formed (CCHA, WCHA) - I doubt they wanted instability in Hockey East as well.