The denominational HQ of ECUSA is actually organized as a "mission society" with all the dioceses as voluntary participants. Until the 20's or so the Presiding Bishop was actually the senior diocesan until they decided to organize on a corporate approach.
You're right. This isn't a slam dunk in any event. The only one winning this one are the stinkin' lawyers again. There is going to be a fight literally over billions of dollars of real estate and pension fund money.
The Pension Fund is another matter. It's a separate unit. From what I understand, you are vested after 5 years so most clergy could bail.
. . . it's happened before, after all . . .