I'm bored with all these threads on who we should admit as a member and how the divisions would line up. Let's think into deeper, more pointless speculation instead.
If we poach a BigEast team, who does the BigEast replace that team with? Say we do get Pitt, Syracuse, or Rutgers. That leaves the BigEast with 7 football teams, and they'll almost definitely want to bring it back to an even 8. They'd have two or three general options in poach a MAC/CUSA/WAC/SunBelt team, convince one of their basketball teams that play FCS to be promoted to FBS (live Villanova), or try to strong arm Notre Dame, a BigEast non-football school, into joining in football.
I think they go with the first option with one of UCF, Marshall, or Louisiana Tech (in descending order of desire). UCF doesn't have long term success, but this year might be a sign that good things are on the way. They'd also provide USF a intrastate rival. Marshall would be similar but with West Virginia, it would just less solid recruiting than a school in Florida. Louisiana Tech is a wild card as they could also help expand the BigEast footprint, and I'd see them leaving the WAC pretty quick. Their isolated from the rest of the league as it is by a couple thousand miles.
If we take an ACC team, I think they have to poach someone from Conference USA. I'm not sure they have the prestige to cherry pick from the BigEast anymore. I think the natural choice is East Carolina, but I think they would also take a strong look at Memphis. Memphis would offer better basketball prospects with meh football.
If we were to poach a Big12 school, they've got choices in the Mountain West, particularly TCU, Utah, and BYU, and they've got Houston in CUSA. TCU probably makes the most sense, but I'm not sure they are the best overall package. Utah and BYU offer better across the board athletics. Any of them would be a great pick-up if willing to move. Houston makes a bit of geographical sense, but I don't think their sports programs are big time enough just yet.
If we upgrade a MAC team, things get tough. There aren't any teams in the Midwest really available. The closest one might be fledgling Western Kentucky. The next closest would be Middle Tennessee or Arkansas State. Another option (pun unintended) would be Navy, or even Army. They're not that geographically close, but neither is Middle Tennessee State or Arkansas State.
I don't see us stealing a PAC10, MWC, CUSA, WAC, or SunBelt member, but if you think you could see it happening, I'd be interested to hear what you would do for one of those.