Hence, St. Thomas concluded that the Incarnation, Death, and Resurrection of Jesus Christ was not just a salvific act on the part of God, but had to serve another purpose as well. If I remember correctly, he postulated that the Incarnation -- aside from the redeeming aspects of it -- also served as a perfect (in that it was Divine) example of humility, compassion, and mercy for mankind to follow. In assuming a human nature, Christ served as a perfect Teacher for the human race because God was no longer a "distant" entity (in the limited capacity of human understanding) occupying a place beyond the comprehension of human beings.
Along these lines, the most remarkable passages in the New Testament are those that describe the Temptation of Christ by Satan after He had been in the desert for forty days. If you read that dialogue carefully, you'll see that Christ "resists" the three temptations (the word "resist" is utterly meaningless in this context, since Christ was incapable of sin) not in a dismissive manner by asserting His own power over Satan, but by responding to Satan's temptations in ways that a human being was fully capable of responding.
Although the Bible clearly commands that the Lord is to be worshipped as Supreme God, and no other shall be put before him, it does not say that no other gods exist. Further, although the Lord may be omnipotent by human standards, that does not mean he isn't bound by certain 'rules', whether self-inflicted or imposed by the existence of other gods.
Indeed, since God and Satan seem to have been battling over the human race since time immemorial, it would seem that if God were truly omnipotent and didn't want Satan to exist, He could simply make it so. Since He has not, there must be a reason. To my mind, the most reasonable explanation is that God is bound by rules of some form, and thus had to do things the way he did. As to what those rules might be, I can't even guess except to note that He seldom performs miracles for which there would be no plausible explanation. If a bus loses its breaks and is carreening down a twisty mountain road, God might add a small rock in the road so as to change the bus' momentum just enough to keep it from going off a cliff, but he won't spontaneously turn the bus into an airplane. The effect may be the same (saving the people on board the bus) but the former would leave open a "rational" explanation (i.e. that the people on the bus simply got lucky).
I think more and more these days of Jesus's sacrifice in the crucifixion not as a juridical event but existential: not a revelation of what he did, but what he is.