It is a fact that the immutable principles of justice will be meted for mercy cannot rob justice otherwise order and growth would quickly turn to chaos and decay; cause always has consequence and it has to be the same for everyone.
We all know and understand that God has all power and knowledge and can do anything He wants to do, BUT, that does not mean that there are some things He will not do because of the consequences thereof, example: he will not cease to be God. If it were as simple as wielding power and creating everything without free will then why not just create a whole slew of harp playing angles and call it good?
There has to be a plan playing out of a necessity and that means requirements, conditions, and responsibilities, even those that God himself will not unjustly circumvent. He did manage to circumvent the demands of Justice with regard to sin by providing a savior, a perfect man that paid the dues of justice (don't ask how it was done because we cannot comprehend that) therefore tilting the odds in His favor because now justice demands that things be balanced again and therefore Jehovah was able to create a path around sin but we must keep his commandments or we must meet the demands of justice ourselves and that is something that a sinner cannot do.
Now keep in mind that there are several things happening at the same time and they all must work together; mortal probation is one and accomplishing the atonement is another and there are more but you get the idea. It seems unfortunate that people, when considering the requirements of one goal fail to consider that sometimes a path that seems simple enough to the goal, and therefore unnecessarily varied, is exactly as it needs to be because all things have to work together for the whole plan to come to a successful fruition in one eternal round where we can, as heirs to a living God, become like him and start the whole thing over again for our own eternal families. That is how God, who already has everything, can have eternal increase - The family. But keep in mind that the power of God is not something that he will hand out to unworthy children who will abuse it to their own destruction and that of others; so here we are working our way toward the ultimate goal in a plan that must be as it is or everything would come to a screeching halt and all ordered creation would cease to exist.