Well, American and overseas UMs are roughly equal in numbers, about six million each. If the vast majority of Annual Conferences or churches of the Central Conferences were to join us, there'd be at least five million of them -- and growing.
Meanwhile, perhaps only a dozen American Annual Conferences would leave as wholes, though many individual congregations throughout the US would leave, to be gathered into new Annual Conferences. A generous estimation -- generous, mind you -- would see 25% of the American UMC leave. (My own personal guess is 20%, tops, because of the inherent difficulty of bringing people to make decisions on facts they've been avoiding or putting off considering.) Anyway, 25% of six million is 1.5 million members.
Now put those two together: 1.5 million Americans + 5 million Africans, Eurasians, etc. The New & Improved MC would be about the same size as the Rump MC, but the balance of its membership would flip from being a US-centric denomination to being an Africa-centric denomination.
That's not a bad thing. And I certainly hope that in a New & Improved MC, we continue to accord all members, all clergy, all conferences equal status in the connection. But such a Connection will have to acknowledge that its center of gravity has flipped.
The new denom will have much less general church administration, but it will still have to have some. I see a lot of meetings being done electronically. But I also see many meetings -- like General Conference -- shifting to Africa and other places much of the time. What general church committees there are will need to have many more Central Conference members.
How we budget our general church expenditures will be affected, too. Central Conference support should be a much larger percentage of our general church funds than it has been under The UMC. If we want to fund mission, if we want to fund growth, then we need to make sure that the Central Conferences have the funds they need to function, not just concentrate on planting churches in America (though that, too, is a major need).
Not only that, but the missional priorities of non-US (mostly, African) Methodists will come to predominate in the church. Non-American thinking about many issues besides sexuality will be a much greater part of the conversation (remember, Africans and Eurasians may agree with us doctrinally and morally, but they are not necessarily conservatives in the American political sense). This is also not a bad thing, but it will of necessity make us Americans -- who are used to thinking that everything revolves around us -- have to grow in our understanding of who we are as Methodists. We will have to look beyond ourselves and recalibrate how we do church.
It will be a challenge. But I think it will be good for us.