Sorry, late reply and not much time... Just wanted to point out that yes there are cases where unarmed folks are a real threat (Chuck Norris et al, or the severely deranged or psychotic, say due to substance abuse).
But mostly the mere fact that LEO are armed should be sufficiently threatening to subdue and solicit cooperation of unarmed individuals. So when shots are fired in such circumstances it merits rigorous scrutiny via a transparent investigation.
Second, the Grand Jury system as I understand it is a bit of a quirky thing, discarded in most places except the U.S. It was meant as a protection of the public from excessive use of executive power, but arguably used in cases such as Ferguson to the opposite effect. Why not simply a regularly prosecuted case?
Finally, your argument that bodycams will mean that "friendly" and informal police actions like letting people off with warnings for minor offenses... That is a good thing. Because it is arbitrary judgment on the part of the officer in question, as to what constitutes "minor" and when to exercise such leniency, and as such is subject to bias. That you would mention this suggests to me you probably don't belong to a group regularly considered victims of the corollary "bad" kind of police bias.