My understanding of Childs' canonical criticism is that it allows one to circumvent difficulties brought about by historical criticism. With Childs a lack of historicity is not a problem. The canonical form of the Bible is that what God wanted to communicate to us.
Canonical criticism views the final canon, the way the scriptures ended up being as being inspired. God controlled what's in there. As far as historicity goes there are many examples where God can "speak" to us simply through a story regardless of the fact that it is historical or not. Think of the parables of Jesus for instance.
Whether or not the scripture requires itself to be historically accurate is another question. I'm operating on the premise that both situations occur. Some parts of scripture expect to be considered historically accurate and others do not.
Part of the difficulty from our perspective is that we live in a culture where the expectations that are placed on writings may or may not coincide with those of the original writers. Take the gospels for example. A person from our perspective would expect a book such as the gospel of John to measure up to historical or biographical works of today. One thing this would imply is chronological accuracy. But the Gospels do not follow this pattern as closely as we would hope. There are things that do not follow a strict chronology. It is also the case that the Gospel writers were selective with the material they reported. There is much to be said for the position that they, in fact, chose their material carefully in order to make a theological statement. Similar things can be seen in the Old Testament where historical situations are reported differently depending on who wrote the book.
All of this doesn't make the Bible uninspired or wrong—it's just that some of our presuppositions regarding how it "should be" need to be questioned.
A few remarks about Gesamtbiblishe Theologie. The term biblische Theology (biblical theology) varies in meaning. It can refer to the Theology which is contained within the Bible - This can include results stemming from historical-critical reflection of the biblical texts. It can also refer to A theology which is in accordance with the Bible. These two definitions were put forward by Ebeling (RGG, "Biblische Theologie"). The entry in the German Wikipedia lists a third definition: The exposition of biblical texts in the overall context of the biblical canon. (Die Auslegung der biblischen Texte im Gesamtzusammenhang des biblischen Kanons)
I presume when the term Gesamtbiblische Theologie is used it refers to the third option. I'm no expert in this area but I can think of two areas where it could have an effect. The historical-critical method has led to fragmentation on two levels. 1.) The texts themselves are viewed as fragmentary works which have been constructed over a period of time and thus contain many influences. 2.) This has led to theological fragmentation. One can speak of the theology of Paul, John and Jesus in the NT. In the OT one can speak of the influence of the priests, the jawist, the elohist etc. Each had thier own agenda and theology.
Whereas the historical-critical approach may have left things in a fragmented state, canonical-criticism is a means of putting things back together. Canonical-criticism can accept the results of historical-critical research but still posit that God is behind it all and somehow a unified message can be derived. The German Wikipedia Article seems to indicate that Brevard Childs (the "father" of canonical criticism), although he places much emphasis on the end form of the biblical canon, he also holds the development of the canonical text to be theologically relevant. For instance, one could ask the question, why did God allow certain elements of the Jawist position to be included as opposed to Elohist positions.
(Again, I'm no expert on this stuff. I've had some very modest exposure to Childs and canonical-criticism. These are just some thoughts I've had from afar.)