Sure. I'll bite. The problem is with a justice system based on plea bargaining run amok (I had a nice reference, but I can't find it...) This leads to a justice system where almost no cases go to trial as the risk for the defendant is much too high since the prosecutor will often skew the risk by offering a sentence reduction of a factor of twenty or more (in the case of Aaron Swartz an even one hundred!)
Any prosecutor that feels that society is safe and justice is served if a defendant agrees to six months in prison, but will call for fifty years as a punishment for going to trial, should be (at a minimum) fired, and a system that thinks this a reasonable approach to meter out justice should be taken out back behind the shed and be put out of its misery.
This leads of course to many innocent people pleading "guilty" (note that the quotation marks are real as you even have that abomination called the "Alford plea" where you can plead "guilty but not really". WTF?)
Now, if for practicalitys sake you wanted to sugar the deal to entice the guilty to confess, then sure, you could argue for a deduction. Say 10% or 15% or something. Not 99%...
In Sweden at the moment we have no plea bargaining, no immunity from prosecution for in turn for providing evidence/being a witness, no juries (laypeople take their place, that sit for a set term and hence can gain some experience), no electing judges and prosecutors (last place on earth you want a politician), and the state provides for your defence (i.e. they pay the lawyer of your choice according to set standards, we don't have any public defenders or something like it).
Now, there is pressure to change that, as we're always looking to what the US does, esp. when it comes to pleas and immunity. You can guess the political persuasion of those shouting the loudest for this change. They're not usually the people most famous for thinking everybody should have the same opportunities regardless of what cards they were dealt when they first sat at the table.