You'd have to go per-region first to avoid a major redesign on the provider (the API is also per-region). I can see something like a `controlled_resource_types` list attribute on the provider that you could set to e.g. `[aws_instance]` to inform the provider it needs to compare the list of resources of the specified type to the state.
True. That'd be fine though, if you wanted to be really thorough you could just specify a provider for every region and only actually 'use' the ones you wanted, the others just serving as a dummy to enforce no resources.
