Is it practical to give weapons and combat vehicles to under-qualified but readily-available individuals to enforce laws they don't understand (let alone have knowledge of) like we do now?

It's not. We just accept it as a default because it's easy to dismiss something obviously good (making sure police are mentally stable, law-aware, and held to a level of scrutiny commensurate to the job) because it may require effort.

Someone being handed a gun and told to go "keep people in line" should be held to an almost absurd standard before ever being let on the streets. That we don't already do this speaks volumes about the underdeveloped state of our civilization (despite our hubris to the contrary).