There is no viable feedback loop at this time. The FBI will get involved if there is a consent decree. This provides oversight, but that requires a Justice department that will investigate police departments. You see this happen after a litany of civil rights violations. But Sessions and Trump have made it clear that that won't happen. Maybe Congress will get involved after the midterms if things change or if there are mass protests. However, since police departments are local you might be able to put pressure on city councils and the mayor / maybe governor to make some progress.

But there should be better training but that will probably only happen if juries start to decide that "being fearful for your life" is not a sufficient defense.