Lambda actions at an aggregate level are not possible at this time.
The reason CloudHealth is unable to act on Lambda functions on Aggregate level policies is due to the fact that we would not be able to assign an ARN to that function. In a per-resource level policy, we can specify the ARN of the asset the function needs act on. In an aggregate policy, there may be a collection of assets and we cannot provide ARNs for all of them which is why it's not currently supported in the platform.
For more information on Lambda policy configuration, see: How AWS Lambda Functions Work in CloudHealth Policies