Might be a good place to use anarchist theory, actually, since with anarchism a power vacuum makes the difference between an anarchist society and a failed state. Even if you lean more ML, the way that a communist society would function after the withering away of the state would probably look similar enough for this to provide useful insight.

Mutual Aid (the book) probably has everything you need. A power vacuum would essentially be unfulfilled functions normally undertaken by a government, and you'd have to make sure the community as a whole takes on all of those functions so the power vacuum is filled and nobody can step in to exploit it. Like, look at Cherán in Mexico. They got rid of government and police involvement in their community. They also didn't leave a power vacuum, because they took over those functions themselves, and kept the people involved in the process through direct democracy. Moreover, they are doing a better job than the government or police ever did, and have stopped the cartels from illegally logging.