You're not the first person I've seen suggest this, and I'm baffled by the logic.
Grand Juries have an especially hard time finding anything wrong with police conduct and are routinely used to "legitimize" questionable police activity.
I'm not ready to agree to eliminating them but it isn't hard to understand why someone might throw it out there as an idea.
No, it doesn't, because eliminating grand juries does not eliminate the gate to a full trial; criminal cases in which that function is not served by the one-sided, prosecution-controlled grand jury process in which the target is not entitled to have representation, cross-examine witnesses or challenge evidence, present evidence, or even be informed that the process is taking place have the function served instead by a preliminary hearing in which the defendant is entitled to all of those things.
The grand jury indictment as an alternative to the preliminary hearing otherwise used is not a safeguard for the accused, it is a means by which the society at large (represented by the grand jury selected from among them rather than the judge handling a preliminary hearing) that the actions of the prosecutor in response to serious crimes are well-directed, it trades away protection of the accused for protection of societal interest in oversight of the executive branch by the public.
> You're not the first person I've seen suggest this, and I'm baffled by the logic.
You seem to think that the alternative to the grand jury is no procedural gateway between accusation and trial, which is not the case. Its understandable that, under that misapprehension, the idea that removing the grand jury would lessen the power of prosecutors would be baffling, because it misses the alternative that actually exists and is, in fact, used for those cases where grand jury indictment is not.
Not that it changes the point of your argument, just guessing where the motivation for that statement comes from.