Today to add a new Common ID we need to send a PR to hashicorp/go-azure-helpers, merge and release that, vendor that into this repository (and downstream dependencies) - and then configure it for detection in this repository.
As of v0.67.0 a new commonids.CommonIds() function is available which returns all of the Common ID types defined within hashicorp/go-azure-sdk - meaning that the majority of the Common ID functions defined here) should be able to replaced by this new function - meaning that this function will require updating
This would mean that we no longer need to define the Common IDs twice - and whilst the other steps would still apply (so we'd need to ensure hashicorp/terraform-provider-azurerm and hashicorp/go-azure-sdk had their hashicorp/go-azure-helpers dependency updated before this repository) - this'd remove a bunch of duplicated logic.
This isn't urgent, and I suspect that we may need to leave a couple of them defined in importer-rest-api-specs - but it'd be worthwhile to reduce the duplication.