I had that idea a while back, brought it up with my TBM family and was told that he couldn't help himself, it was his nature to encourage evil and so He'd never give up. LOL, guess Satan doesn't have free agency. He could appear as an angel of light and testify the true of the LDS Church, Proclaim Christ Lord and Savior to everyone and then he'd really screw up the faith part of the game.
and the "Just do good deeds" option didn't test well with our opinion group. *MY* question, which nobody seemed to be bothered to answer, was why do this whole "Mortal existence" thingy anyway? Especially if everything was so hunky-dory in the pre-existence that everyone would want to get back to it.
We wanted to have a body so we could have lots of illicit sex, eat large quantities of great food, and drink copious amounts of alcohol. This would eventually kill us, and we would die happy.
He could gather up all his minions and they could repent and return to God. Then there would be no opposition in all things (according to Mormon spirituality anyway). According to the Book of Mormon, if there's no opposition in all things, God would cease to be God.
So Satan could still thwart and even dethrone God if he really wanted to.
But Satan's smart. So why won't he do that? Because he and God are in kahoots! That's why. They like to play games like rock-paper-scissors with our lives (read Job chapter 1), do some gambling on the side, and generally have it pretty good. They've had their disagreements but otherwise are quite the partnership.
They just want us to think they're enemies just to keep us hopping around trying not to piss them off.