Make it possible to join several iNaturalist Network affiliations at once without losing previous affiliations

This request comes from the following discussion.

It appears that if you choose to be affiliated with a specific iNat sub-region (eg. iNat Finland, iNat Canada, iNaturalist, etc) you lose any previous affiliation and are locked in to the one affiliation.

For those of us who travel often, have specific interests in multiple regions (eg. live in one, but have work/research interests/family, or are simple very interested in multiple regions) it would be nice if it were possible to be affiliated with more than one iNat sub-region at a time.