I wonder if it would work to have the police split into two separate units (kind of like how the swat team is separate). So you have a general response police unit, which is unarmed or lightly armed (taser / nightstick, etc). They would respond to most situations, and would be highly trained in de-escalation techniques. Then have the backup units be the muscle. In situations that they feel are dicey, the backup could show up at the same time, but hang back unless they are needed.

The main problem with this is that they don't know what they will be facing when they get to the scene. In most cases things go smoothly (traffic stops, domestic calls, detective work). But when things go bad they go bad quickly.

Of course if the first-responding police wore different uniforms, then there may be less chance of escalation. And people would know that as soon as the first responder has to call backup, then things will get really bad for them -- kind of like if you harass a social worker, you will have a very bad day.