In your scenario, Feature B should not have been promoted into the development branch until everyone agrees it's going to be shipped. If it got into development without everyone's approval, then that is a business process problem, not a CVS tool problem.
At my last job, we had a 'gorilla' that had to approve every commit, and it was his job to coordinate between the project managers and the developers as to what was allow to be promoted to prevent exactly the scenario you described. It also had the benefit of making developers describe each commit clearly so that the gorilla could understand the change, which made looking at the commit history some time later (months/years) quite a bit easier too.
