Garrett Green wrote in Imagining God that it doesn't matter if the exodus "really" happened. Scripture's authority lies not in how accurately it depicts "the facts" but in its unique ability to renew our imaginations with metaphors which are faithful to the kind of God God is. Scripture renders to us a "paradigmatic imagination", a lens through which we see God, the world, and ourselves in God's world. It is this seeing that constitutes religion.
...religion is imaginative, religious language is metaphorical, and theology is hermeneutical.
That is to say, theology is the interpretation of metaphors that have been been revealed from the imagination of God to the imagination of God's witnesses - most significantly, the witnesses who saw Jesus as the imago dei.
With our imaginations as the locus for God's self-revelation, Green has attempted to move beyond the dualism of "fact" or "fiction", of "illusory" or "real". One of the memorable quotes in the book is the paraphrase of a sentence in Paul's first letter to the Corinthians:
The illusions of God are more real than the realities of men.
Obviously there are a lot of words that Green fleshes out -- imagination and metaphor to name two big ones -- but how does any of the above strike you? I can't help but think of Caird/Wright's dictum, "Christianity appeals to history, and to history it must turn" and find that what Green says is very much at odds with what these eminent NT scholars propose. Of course there is the slippery slope of moving from the exodus as something whose "real" happening doesn't matter to the resurrection as an event whose "really happened-ness" is irrelevant for faithful imagination. But then the book of Exodus and the Gospel narratives are different books with different purposes. Suffice to say, slippery slope arguments are usually red herrings.