Maybe I'm spoiled, but this seems like a solution in search of a problem. Is it truly common to have separate environments described by independent copy-pastes of the conceptually-same code, rather than one configurable CDK construct or Terraform equivalent? If I heard "When someone makes a change to the code for one instance, they copy or merge the change to other instances. The process for doing this is usually manual, and involves effort and care to ensure that deliberate differences between instances are maintained, while avoiding unintended differences." rather than using a deployment pipeline, I'd run screaming.