As a follow-up to EZP-25484, we've discovered that since Content & Location remote IDs need to be handled implementing a dedicated strategy for them, the cleanest approach would be to introduce dedicated Solr Field Type e.g. remote_identifier as well, defined in the same way as identifier.
Wasn't done as a part of the mentioned task, because it would force Users to re-index content.

It's safer to introduce this in the next minor release. Targeting minor, not major version because there's no explicit BC promise on Solr schema for eZ Platform.