If sentencing guidelines were ratcheted sharply downwards, plea bargaining wouldn't have an extortative effect, because prosecutors wouldn't have the latitude to pursue outlandish sentences.

However, if plea bargaining was outlawed but sentencing guidelines remained as they are now, sentencing and criminal procedure would remain unjust for the majority of defendants, who are ultimately guilty but don't deserve outlandish sentences.

Both policy changes are very unlikely, but for different reasons.

Plea bargaining won't be outlawed or curtailed because doing so would require allocating a huge amount of money to the court system, which is already overtaxed. Preempting an argument nobody has made: that's not "their problem, not ours", because what we'd really be talking about is years and years of delayed trials during which people will be held in confinement anyways. Look at China for an example of a system that has that problem in a big way.

Sentences won't be ratcheted down because there's never a political upside for doing that. That's obviously tragic.