So the civilian watch would effectively only have lethal force to stop a threat then? All of those things have a purpose. Armored vehicles for example are most often used to approach armed suspects who have holed themselves up in a defensive position without risking seat or police lives. Stingrays are used to track gang, cartel, weapons dealing, and terrorist activities.
You could argue that only federal entities should have that power, but then the FBI/DEA/ATF would inevitably fill the power vacuum and take over a lot of roles that would otherwise be done by police. The alternative of course if that we simply don't use Stingrays, armored vehicles, riot shields and rubber bullets, but then a lot of crime would go unpunished either from lack of information gathering or simply from fear of death (for example, a civilian with just a gun would have a much higher chance of death trying to free a child from an armed abductor that a swat team with armored vehicles, bulletproof shields, etc.)