I'm not sure there exists a 'fair' system that can operate without some sort of jury, but as long as there's a human element no trial has a guaranteed outcome.
In addition, you’re oversimplifying why people agree to plea deals. Lawyers are expensive, and a poor person might prefer to just go to jail for a short time rather than spend thousands of dollars for an uncertain outcome. Even if they are confident they would win in a jury trial, that’s still thousands of dollars in fees to their lawyer.
This was literally my point, jury trials are uncertain. Except it applies even in cases where people have millions of dollars to burn. A possible 40 years in prison or 5 years under house arrest?
Though of course, as I was typing I was reminded of the Android case. And countless other cases where a judge was the unknown factor, so really, it doesn't matter how much lawyers cost. Any trial will always be an unknown until someone can code a deterministic judge bot.
I really advise you to read up on some of the literature about plea deals; there are very few people who think that they are something we should have at the scale that we have them, or something that we should have “as long as” we have jury trials. The prevalence of plea deals in the American criminal justice system is primarily due to the fact that there are simply too many crimes for our courts and public defenders to handle promptly (an incentive for prosecutors) and that legal representation is so expensive (an incentive for defendants, and also for shady prosecutors).
Here’s a blog post on the ACLU’s website about it: https://www.aclu.org/blog/mass-incarceration/its-not-just-pr...