None of us know what size gap would induce ND to jump, I'm merely pondering how to increase said size by a fair amount.
At some point, they'd jump, or become an afterthought.
A few thoughts:
First, it appears that stubbornness is a major reason that Notre Dame is not already in the B1G. That being the case, I think that trying to force their hand by refusing to play them would backfire because it would (quite reasonably and fairly) tick them off which would only harden their stance and lead to them digging in even more.
Second, I honestly don't think that they are a good long-term addition. They are presently a super-helmet no doubt about it. In the long-term, however, I see them as a diminishing brand for two reasons:
- Religious identification is a consistently declining part of how Americans see themselves. As such, I see their long-term fanbase shrinking as there are less and less people for whom being catholic is central to their self-identity.
- IMHO, a big part of the LARGE Notre Dame anti-fan group is specifically because they are NOT in a league and appear to be treated as different/special*. This disappears the instant that they join a league.
WRT Notre Dame being treated as different/special:
I attended the tOSU/Miami BCSCG back in 2003 (2002 season). In the stadium prior to the game they ran a BCS promo video on the jumbotrons. The video included a little snippet on each of the then BCS leagues. As each BCS league was listed the video showed footage relating to that league. Then, after listing all six BCS leagues came "and Notre Dame" while footage of the golden dome ran. EVERYONE in the stadium booed. Even today, 20+ years later probably the only thing from that game that tOSU and Miami fans would readily agree upon is that Notre Dame shouldn't have been treated (within the video) as the equivalent to a league.
I've never liked Notre Dame but my intense distaste for them sprang from that moment. Treat ND as equivalent to my school, ok fine. Treat ND as equivalent to my school plus Michigan plus Penn State plus Wisconsin plus etc, NO.