I think the original release format of one primary source with general setting information and additional regional books that go into detail about the locations in different areas was a pretty good one. You can get the main campaign set and the sourcebook for whatever region you want to play in, with the other ones being optional.
I would do them like this:
Savage Frontier (North of Daggerford)
Western Heartlands (South of Daggerford, East of Cormyr)
(Eastern) Heartlands (Cormyr, Dragon Coast, Sembia, Dalelands)
Central North (Moonsea, The Vast, Vaasa, Damara, Impiltur)
Unapproachable East (Narfel, Great Dale, Thesk, Aglarond, Rashemen, Thay)
[Southern Sword Coast (Amn, Tethyr, Calimshan)]
Moonsea is difficult to place. It seems more connected to the Dalelands, but the Eastern Heartlands are already very packed.