Dataprovider For Related Activerecord Models

Is there an easy way to construct a dataprovider that returns objects related to another object?

I'm basically looking for the simplest version of this function:

/**
 * @param CActiveRecord $model        The primary model whose relations the provider will retrieve
 * @param string        $relationName The name of the relation we want to retrieve
 * @return CActiveDataProvider Provider that returns the related models
 **/
public function getRelationProvider($model, $relationName);

I do not want to return an array of related objects. Some instances may have thousands of related objects and I'm concerned about performance issues. (Sidenote: is that a valid concern? Should I just use CArrayDataProvider?)

I have considered this solution but it seems somewhat complicated:

• Parse the relation declaration into a criteria object
  
• Merge that criteria with the DbCriteria of an instance of the related model
  
• Construct a dataprovider using the updated instance

I'd like to avoid that if possible. Any ideas/patterns for solving this problem?