The issue of divine sovereignty is already settled. It was at the cross. The resurrection was the proof of it. The issue is settled, evil lost. I don't understand your statement " If intelligent life elsewhere did not rebel then there would be no reason to settle the rebellion sin issue here on earth ". All created beings have free will. Because most didn't fall in the past doesn't mean they won't make terrible choices in the future. That is why the full measure of disobedience is being played out on earth. All of the ugly, brutal, and painful results are an object lesson to the universe on exactly what happens with the abuse of free will. It is a lesson that will, in some form, be remembered forever.
If Adam had chosen to remain faithful we would Not have the sin issue to settle here on Earth.
If elsewhere there was a 'faithful' creation, then the issue would have already been settled.
Satan challenges all of us (Job 2:4-5) touch our ' flesh ' (Loose physical health) and we would Not serve God.
If there was 'faithful' intelligent life elsewhere there would be No need to settle that challenge here on Earth.
Under adverse conditions both Jesus and Job proved Satan a liar and so can we answer that challenge.
I do see what you mean by already settled as far as God's Sovereignty because Daniel 2:44 shows that God's Kingdom government is the coming victor. By my saying 'coming victor' is because Daniel 2:44 is yet to take place.
The coming ' time of separation ' on Earth of Matthew 25:31-33,37 is yet future. At that time then the world will see who is the rightful Sovereign thus never again will anyone question God's right to govern.
Any comments about Ezekiel 38:23