Ethics and the Exodus

Bnei Yisrael are about to leave Egypt, and in fulfilment of God's earlier statement, they ask their Egyptian neighbors for vessels and clothing. We return to God's promise to Moshe at the burning bush about women borrowing from their neighbors, and that Moshe is to request permission for  Bnei Yisrael to go to the desert for three days. Why is all this deception necessary? Why is the request not more upfront? What do we do when we are faced with apparently competing values and questions about Divine morality? Is there a deeper ethical value behind this structure of events? If one of the goals of the Exodus saga is for Pharaoh to recognize God out of his free will, then Moshe's request of Pharaoh must be something reasonable.