requirements were essentially a good thing.
I don't know if it's still true, but a couple of decades ago Kansas City, MO, required that anyone working for the city live within the city limits.
I currently live in Santa Fe, NM. There is not a requirement that police officers (don't know about any other job areas) live within the city limits. Which means that a significant number of our police live elsewhere, mainly in the northern suburbs of Albuquerque. Here, the essential problem is that Santa Fe is relatively expensive to live in, especially as compared to ABQ. Clearly people in this state haven't a clue about cost of living in other parts of the country, but that's probably a separate discussion. Anyway, too many of our police do not live inside the city they are sworn to protect. So yeah, I say that a residency rule is actually a good one. It may well be that for that residency rule to be workable, salaries need to be raised. I'm sure that's true here in Santa Fe.
I used to live in Overland Park, KS, which is a suburb of Kansas City, MO (and please note the different states) and the second most populous city in Kansas. You've probably never heard of it, in no small part because people from there tend to say they're from Kansas City. Which is in Missouri. I've NEVER been willing to say that, partly because KCMO residents tend to disparage Kansas and Overland Park in particular, specifically pointing out our higher taxes. When I point out our vastly better schools they get defensive. I wonder why. My years in OPKS fed into very strong opinions about a lot of things, including where you live vs where you work. There is not one simple answer, and of course people cross city, county, and state boundaries for jobs, compared to where they live.
This is a complex and complicated issue. But I will suggest that if St. Louis is having trouble hiring people who live within the city to be police officers, they need to take a long and hard look at why that is the case, and try to solve those problems, rather than having outsiders become police officers.