Most are protected under Civil Service regulations.
Bear in mind that whenever cuts loom (even minor one’s) agencies act swiftly to shut down things like national parks, threaten delays in social security checks, stop processing applications, etc. They will claim that resource constraints prevent them from performing vital services and they will get their friends in the media to launch a campaign of disinformation to rile up the people. Agencies are well-schooled in the art of protecting themselves.
Yes, there is such a thing a buyouts but generally that only applies to those with a lot of years of service. And even then, they may not leave.
The point is, it won’t be an easy thing to accomplish and it will take a lot of thoughtful planning.
Sure it is. You eliminate every dept executively that you can and legislatively where needed. Wholesale.
Then you rebuild new ones only where, staffed by, those needed. The problem is analysis paralysis.