The main efficiency problem of the federal government is detachment, or the not-my-job mindset. If you really want to see a fast, efficient federal work force, get everyone in the department to start communicating and working together on everything regardless of title or seniority. In every department there is someone slacking off and someone over tasked, and those roles may change over time due to the chunkiness of our work (that is to say the workload is intermittent and an individual's workload varies from day to day or week to week). This chunkiness is an inherent feature of qualitative work, and overcoming the problem requires providing an incentive to finish all projects, regardless of size and scope, as efficiently and quickly as possible.
My recommendation to achieve this without massive processes or oversight is to motivate and empower the employees to do it themselves. For example, you could give the option to all branches, departments, groups, etc, to work a 7 hour day instead of an 8 hour day with full pay. Then you make a couple of additional rules:
1. You must be able to show everyone in your group how your work could be finished in a 7 hour day. Meaning they know what you are doing and could do it themselves if need be.
2. Nobody leaves unless everyone in the group can leave, including supervisors. This means those that have nothing to do at the moment have to help others in order to leave early and nobody can hold on to task, working on one project too long to keep themselves busy or rake in the over time.
My point is this, trying to create some universal rule or process is not going to solve our efficiency problems. You have employed 2.15 million people, these people are smart enough to assess their situation and make improvements that work for their specific situation. However we are hindered by coworkers who don’t care, are too busy, or tried it before and gave up. We need some kind of unifying goal that is going to make us work as a team. If you were to implement this change I think you would see a radical improvement in the productivity, efficiency and work culture of the Government/DoD.