The IG defines the resourceType extension, which is useful but not widely used yet. It would also be useful to define operations or search patterns to better support canonical resolution:

• Search at the root by url and possibly version (given any canonical URL, with or without version, return any resources that match that url reference)
• Given a resource, how do I know whether it is a "canonical" resource

(Works) https://server.fire.ly?url=http://test.com
(Doesn’t) https://hapi.fhir.org/baseR4?url=http://test.com

https://server.fire.ly?url=http://hl7.org/fhir/ig/opioid-cds/PlanDefinition/opioidcds-07&version=0.1.0