Wouldnt that court and the overview be again a risk? And if people could change a provate armies boss then this army is useless since they need the power to stop an uproar.
And people fighting an army to change the boss? They would need weapons for that and they would face an army then. Of course, if other militias work, then they could help. Question is if enough people would stand up since i believe the majority would stay in fear.
Maybe the key would be the militias controlling each other. But even then... factions might build with generals who think different or follow a leader that promises them things. Even without an instant war, things could slowly turn bad. You cant intervene because the problems arent big enough but at one point the factions could turn violent and they might be so big that its a real problem then.
No, the citizenry would be armed, it would be a free society. The militias role is only to provide an organized defense of that land.
So if 2 burglars would attack your house you would grab your gun and deal with them. But if 20 burglars would attack it, you would call the militia.
It would both fill the role of police and military in that region.
So the question is weather if 1 militia leader becomes a tyrant how to stop him?
Very simple, the citizenry itself is armed, so the leverage is pretty equal. Also since the militia is from local citizens, they are much likely to disobey as the community doesnt like him. So at this point if in an objective court it is determined that the garrison commander is a tyrant, and it is ordered to leave office the following can happen
1) He wont leave, and will order his henchmen to continue the tyrrany and fear in that region
THEN
A) the citizenry will revolt because all of the have guys and they could easily combat that garrison of 3000-4000 soldiers
B) due to the pressure, the soldiers will disobey, try to coup-de-etat him, or just resign from duty, so the tyrant would be left powerless
C) you call in a neighboring militia or form a temporary coalition of them, which will be disbanded after the conflict is over, to overthrow the tyrant with force and possible a small battle has to take place. Now this is the worst case scenario so the other 2 are more likely to happen
2) He will obey the court order and resign, giving up all power, and possibly face charges because he was a tyrant
3) He will try to bribe the court or threaten it to change the ruling, but this can bring that court's legitimacy in question, and since it's a private court i dont think it's owners would risk this
So this is a perfect example how to handle these unconfortable situations.