Even if one would raze all the POCOs, it doesn’t matter at all. The moment they leave, the POCO empire is re-installed within a week.
The only solution that would work long-time is to make POCOs fuel-dependent like every other corp-owned-profit-generating structure that is anchored in space. They must be refueled every some weeks, just very little amounts, so no big costs apply, but the effort of refueling them again and again could only be undertaken long-term by a local group that actually lives there with active members. Anyone trying to create some “holding corp” with many hundred or a thousand POCOs that are protected by some huge fleet that can travel anywhere if one comes under attack would despair over the insane amount of fuel-runs they had to do every day.