I just wanted to follow up on this.

Github 110 is now closed as we've finished removing explicit references to
regions in the Abacus API in favor of a more generic namespace/scoping
mechanism. With these changes, organization ids, resource instance ids, etc
can include a namespace/scope allowing you to ensure they're really
universally unique across your multiple CF deployments (if you're
paranoid...)

For example the following ids will be happily accepted:
a3d7fe4d-3cb1-4cc3-a831-ffe98e20cf27
us-south:a3d7fe4d-3cb1-4cc3-a831-ffe98e20cf27
my-deployment:foo:bar:xyz23:a3d7fe4d-3cb1-4cc3-a831-ffe98e20cf27
...

We're keeping the existing region field as optional for now in the usage
schemas to avoid breaking the folks that use it, but it's not needed
anymore, and I'd like to remove it as well at some point.

HTH

- Jean-Sebastien