Good for the ABA to advise Congress to tone down the rhetoric and put down the pitchforks before finalizing changes to the UCMJ.
The imposition of mandatory minimum sentences is dangerous to the rights of our service members. So is withholding a service member's right to request a military panel (jury) to decide a sentence rather than a military judge.
The dangers of statutory mandatory minimum sentences have been well-documented, especially in recent years. Every case is different, and to legislate otherwise to take away judgment calls in an individual court is not justice. At any given court, the judge and the jury are far, far more able to fairly judge what the outcome of the case should be - for Congress to brazenly institute mandatory minimums serves only to tip the scales.
Regarding the issue of a service member's choice to have the judge or jury impose a sentence - this right is as old as the UCMJ itself. And it exists for a reason. Sure, in civilian court the judge almost always imposes the sentence. It is also correct that the judge may have a better grasp of the "going rate" for typical offenses. But, giving the military accused the choice allows for more fairness - for instance, if you were facing a court-martial and drew the "killing judge" known for imposing unusually harsh sentences compared to other judges, wouldn't you want to be able to opt out?
Moreover, the entire UCMJ is arranged in a different fashion than a civilian justice system. Part of its purpose is to move cases through to the end with speed - the military has a great interest in finishing cases quickly both because of resources, because military justice works better when imposed swiftly, and because frankly they have bigger things to focus on than carry a case along forever. To achieve this speed, juries can be small and jury verdicts need not be unanimous. Even for the most serious crimes, a panel may consist of only five members. And no matter the size of the panel, a guilty verdict is achieved if 2/3 of the members vote guilty - in civilian court the prosecution usually needs a unanimous verdict or else it is a hung jury and the trial starts over with a new jury. No such unanimous protection exists for the military accused - the UCMJ wants a final verdict the first time, so 1/3 of the panel may vote not guilty but the result is still a guilty verdict. Allowing the accused to choose between a judge or a jury to decide the sentence is a smart way to offset this issue, and brings more fairness and equity to the process.
If Congress wants to re-work the UCMJ, they need to re-work it all. If they take the protections of the accused away, they should add in the protections that exist in the civilian system as well.