Here is my view implementing business requirements with DDD, Event Sourcing and CQRS.
Applying the same 3 steps for each new requirements let improves time after time the mechanics of each small bubble while it is living in the aquarium of an Event Driven ecosystem along with bigger legacy bubble.
A messaging architecture can become the way to slice the domain in small parts to rapidly give value back to the business and at the same time integrate with existing legacy systems, keeping them as they are or with little refactoring, without the need of lengthy and risky refactoring projects.