Designed for what, exactly?
Mormons have a very elaborate history of the "premortal existence." It follows Milton's verson, with a couple of important revisions.
First off, God the Father is not alone. He's married. Heavenly Mother keeps in the heavenly kitchen, though, so her name doesn't get blasphemed. God the Father and Heavenly Mother had a whole bunch of kids. Us. Two of these sons are more important than the others: Jesus and Lucifer.
Now, God wanted to put all of his children through the steps that would enable them to become adult divinities. So he created Earth and set up the rules for coming back and becoming like him: get a body, experience life, and die. The catch is that you've got to remember that the goal is to get back to God. Then he asked his sons what other parameters should be involved.
The sons went off and came up with their design projects. Lucifer's proposal would program the incarnated souls to march through the various righteous steps: birth, chastity until marriage, church-attendance, joyous death. Lucifer was proud of his proposal, as it would bring all the souls back to God. Jesus's proposal was chancier: he suggested that the souls should forget their origins and destinations, and that they should have choices ("free agency" is the preferred Mormon term). Jesus admitted that he'd lose some, but those who made it back would really deserve to become like God.
Lucifer was pissed, a third of the Heavenly Host agreed with him, and they rebelled, got tossed out of Heaven, and wander the universe without material bodies, wreaking random havok. So it's like Paradise Lost, except that Lucifer here is a kind of totalitarian. Take that, Shelley!
So the Mormon answer to Ophelia's question is that the Designer is only responding to an already-existing condition, and that Designing is happening all the time, on different planets and universes.
The sheer creativity of early Mormon theology has always impressed me.