The partner is an issue for joining the Big Ten, not the ACC. Assuming Texas goes to the PAC 12 (which I believe they will due to pressure from Texas politicians not wanting Texas Tech to get left out of the Power 5), the only real expansion options for the Big Ten are Kansas and UConn. The problem is that both are seen as basketball schools with weak football programs, making it unlikely they get added together. Yes, they previously added Maryland and Rutgers but the landscape has changed since then and adding two bad football schools may not be feasible now. In the end though, if the Big 12 falls apart and the other power conferences expand to 16, the Big Ten might essentially be forced to add UConn and Kansas together because there are no other options (unless they can poach Colorado at the end of the PAC 12's GOR).
In terms of joining the ACC, the accompanying move would be Notre Dame becoming a full member (or UConn could join as a non-football member). I know this thread is about the ACC adding multiple schools from the American but I just don't see the logic in it. As for UConn being admitted as a non-football member, it's an intriguing idea. UConn would clearly add value to the conference in basketball and the ACC wouldn't have to share as much money with UConn as they would if the Huskies joined in football too. As part of the agreement, UConn would become the 16th football school in the ACC if Notre Dame ever joined the conference in that sport.