I've worked with people that put down much more dangerous subjects than some meth head. I've taken part in such operations myself as well.

For any person not armed with a firearm or bladed weapon the answer is simple: You keep them contained without committing to an engagement until you have a sufficient number of people on site (2-4 guys should be enough), then you swarm them with batons and pepper spray. Even the beefiest guy in the world will hit the ground after a solid round of pepper spray and a couple good whacks to the legs and body when they have three guys hanging onto them.

If they have a bladed weapon you do the same thing, but make sure you get vests, longer batons, and more guys. The key is that you want to swarm and overwhelm the subject from all sides in such a way that you can force them to the ground without any individual grappling with them alone.

In all cases, the subject is likely to try to single out individuals in order to attack. Use a baton, pepper spray, a frontal kick, or "running away" in order to keep them contained until you can swarm them. Treat the them like a trapped animal: You want to make sure they can never single out anyone to attack, by constantly controlling distance while you circle them in.

This shit isn't hard. I've worked with 19-year olds that mastered it. These cops fucked up colossally if a meth head was able to start wrestling one of them over control of a gun. This just shows that arming the police with firearms in situations where they aren't necessary just makes the situation more dangerous for everyone involved. If the meth head gets control of the gun... they now have a gun. An unarmed meth head can be dealt with without bringing a gun to the scene in the first place.