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.
That's how the Brits do it and I think the Germans too.
They do all have extensible batons and training in how to use that to defend themselves against somebody who is a bit handy with their fists or waving a blade about while they retreat, as well as training in how to de-escalate.
Even when there's an armed suspect retreating is very often the appropriate thing. Because you've got time and numbers on your side. Why risk getting stabbed (or shot) to make an arrest now, when in the not too distant future the suspect will be asleep and you or your colleagues can trivially disarm them?
There are scenarios when police need an immediate armed intervention, but they just aren't (and shouldn't be) common enough to justify giving every single cop a handgun and the training needed to use it effectively.
Of course the Americans seem to have largely skipped the second part of that, which doesn't help at all.
I do agree with the training in de-escalation though. German Police has a much more extensive training then the US.