I'll certainly post my own interpretive renderings of the commandments, but first I want to respond to your post.
You're right. It would be sadistic to require something utterly beyond achievement, unless the requirement being imposed had another purpose. Let's play with that idea for a moment.
Our problem, I think, is that most humans set the bar rather low. We're content at the personal level to avoid "excessive" sin. We, in effect, rewrite the commandments to fit us.
"Don't have too many gods other than the one God. "Don't lie excessively." "Don't steal enough to really hurt anyone else." On and on it goes. Most humans and societies have little use for "perfection," either as a goal or in practice. It's as if we decided to take up running each day for our health. Only the first day, we find out how hard it is to run at all. Each day thereafter we run or walk a little less. Finally, we reach the point where do not run at all, though we keep our shoes and gear in a bag in the car.
The commandments, Jesus' injunction to be perfect as God is perfect, and the rest startle us. Someone dares try to raise the bar. Frankly, he or they set the bar too high. We can't make the jump. Trying to do so teaches this is so. We're not God, so we cannot be "perfect" as God is perfect.
So...the commandments and the injunction of Jesus (taken seriously) may force us to admit: "I'm only human." This, though, is not an admission of defeat but instead an acknowledgement of our true selves. We were never meant to be God. Humans were never created to be as God. We are made to be, well, human, the children of God. A great, self-imposed burden drops away. Strangely enough, acknowledging our legitimate limits frees us to rely upon God for help, to pursue perfection without becoming paralyzed by our failures, and to get on with our core vocation of caring for the world and others.
Well, enough. I'll look forward to reading your recasting of the commandments, and I'll follow up with my own as soon as possible.