problematic system you propose

How would 'actual harm done' be determined? That would lead to the problem we have now, where 'victims' are pushed into turning on the waterworks in order to get a longer sentence, and psychiatrists talk about how if a child has their genitals touched they may as well have been tortured and/or murdered.
What we really need is for, when a side puts an expert witness on the stand, they also have to pay for an expert witness chosen by the other side. Too often the prosecutor can roll out an infinite number of expert witnesses who talk fire and brimstone, and the defense can't pony up enough cash to put up one devil's advocate. Of course the opposite happens sometimes as well, like when OJ Simpson had a large legal team that outgunned the prosecution.