1 And I, the Lord God, spake unto Moses, saying: That Satan, whom thou hast commanded in the name of mine Only Begotten, is the same which was from the beginning, and he came before me, saying—Behold, here am I, send me, I will be thy son, and I will redeem all mankind, that one soul shall not be lost, and surely I will do it; wherefore give me thine honor.
2 But, behold, my Beloved Son, which was my Beloved and Chosen from the beginning, said unto me—Father, thy will be done, and the glory be thine forever.
I have often wondered, what's so wrong with Satan's plan as laid out in these verses? I like the idea of everyone being "redeem[ed]", and I think that's a worthy goal (even if it's just a goal). Certainly I believe God loves all of His children, so it seems natural to want everyone to make it safely home.
It's hard to be "against" that point of view on pretty much any level. And, really, I'm all for it. But I think there is a strongly implied undercurrent to this situation that, for a long time, I've missed. Satan never had any plans to love all of God's children. Nor did he want them to be "like" him; redemption is different from exaltation, and while I'm not sure if that technical difference is meant to be part of these verses, I tend to think Satan's version of Heaven meant a.) we were all "redeemed", but b.) he was to be the all-powerful God over us forever and we'd never share in the same experiences that he was having as God. So, while his plan sounds nice, it did not include love, mercy, or any sense of having a "Heavenly Father" that I believe in, theologically speaking.
I think this also implies that mercy vs. justice could have been, under Satan's plan at least, a zero-sum game. For instance, I feel that these verses take on a different meaning when we contemplate the idea of having either mercy, or justice, but not both:
25 What, do ye suppose that mercy can rob justice? I say unto you, Nay; not one whit. If so, God would cease to be God.
26 And thus God bringeth about his great and eternal purposes, which were prepared from the foundation of the world. And thus cometh about the salvation and the redemption of men, and also their destruction and misery.
27 Therefore, O my son, whosoever will come may come and partake of the waters of life freely; and whosoever will not come the same is not compelled to come; but in the last day it shall be restored unto him according to his deeds.
I think I'd go a bit further than Alma does in vs 25, namely that Justice and Mercy are, because of the Atonement, married in a way that prevents this zero-sum-game outcome. I feel that vs 26 can be read to support the idea that all "destruction and misery" in life comes from disobeying God's commandments, which IMO is not true. In my experience bad things happen and good things happen to me oftentimes no matter what, and that's one of the features of life that makes this world "telestial". There is not always a logical a -> b when it comes to suffering or success.
Why is it that way? This is one of the features of Satan's plan that gives a bit of comfort, namely that everyone will be redeemed. I've often wondered how he might go about accomplishing this. My current view of Satan, as a person, is that he wants all the trappings of God's power but fundamentally does not understand the "love" part of it. Thus his "plan" was to essentially spell it all out for us, give us thousands and thousands of pages of dos and don'ts so that we would have a perfect guide for how to live life. There was no room for error in his plan, and there is some presumption that there was also no room for growth. Regardless, there definitely was and is no room for love (in the forms of grace and mercy), and that is the main feature that sets his plan apart from God's. This, I believe, is why charity is listed along with faith and hope as one of the cardinal virtues, and perhaps _the_ cardinal virtue:
4 Charity suffereth long, and is kind; charity envieth not; charity vaunteth not itself, is not puffed up,
5 Doth not behave itself unseemly, seeketh not her own, is not easily provoked, thinketh no evil;
6 Rejoiceth not in iniquity, but rejoiceth in the truth;
7 Beareth all things, believeth all things, hopeth all things, endureth all things.
8 Charity never faileth: but whether there be prophecies, they shall fail; whether there be tongues, they shall cease; whether there be knowledge, it shall vanish away.
9 For we know in part, and we prophesy in part.
10 But when that which is perfect is come, then that which is in part shall be done away.
Thus the choice between God's plan and Satan's plan is about far more than choosing to have agency, I believe it's about choosing love in the face of imperfection. Thus "charity never faileth" -- love can be the one constant that overarches all other failings and imperfections in life.