Was the "Already" Dimension of the Kingdom Significant Enough to Motivate Jesus?

For my write-up today on Ben Witherington III's Jesus, Paul, and the End of the World, I'll use as my starting-point something that Witherington says on page 82:

"For Paul basileia [(kingdom)] in the present is God's dynamic saving activity, or his reign in human lives brought about through the Holy Spirit, or the results of that activity.  In the future, the basileia is a realm that believers may enter, but it too comes as a result of the dynamic action of God's agent at his parousia."

So Witherington believes that Paul regards the Kingdom of God as already-and-not-yet: a reality that has a present dimension and yet will have a future fulfillment at the Second Coming of Christ.  And, according to Witherington, Jesus had a similar view on the Kingdom.  At the same time, Witherington denies that Paul and Jesus equated the Kingdom of God with the church.

Witherington argues that Jesus and his disciples were seeking to bring Israel to God so she could avoid disaster.  Witherington appears to hold that Jesus has eschatological motivations for his ministry that relate to the inbreaking of the Kingdom of God.  In Witherington's scenario (if I am understanding it correctly), whereas Paul in Romans 9-11 envisions a scenario in which the inclusion of the Gentiles into God's people will precede the spiritual restoration of Israel, Jesus has another view: that the spiritual restoration of Israel will precede the reconciliation of the Gentiles with God.  Witherington says that Jesus in Matthew 28 envisioned the early Christians going into all the world and preaching first to the Diaspora Jews, which is essentially what we see in the Book of Acts: Paul visits a foreign country and often goes first to the local synagogue.  At the same time, Witherington seems to think that Jesus was not thoroughly optimistic about Israel repenting and that preceding the Gentile worship of God, for Witherington appeals to such passages as Luke 13:29, which envisions Gentiles taking the place of non-repentant Jews at the eschatological banquet.

(UPDATE: I may be wrong in my interpretation of Witherington on the issue of Jesus thinking that Gentiles would take the place of non-repentant Jews at the messianic banquet.  On page 229, Witherington says it's more likely that Jesus envisioned Diaspora Jews, not Gentiles, coming from afar and replacing Jesus' "unfaithful listeners ('this generation') at the banquet.")

Where am I puzzled?  Witherington appears to maintain that Jesus did eschatological things that pertained to the Kingdom of God, such as bringing Israel back to God.  But he simultaneously denies that Jesus believed that the end of the world was necessarily imminent.  If Witherington is right about that, then what was the purpose of Jesus' mission to restore Israel and thereby bring the Gentiles to God?  Did Jesus work in light of the "already" dimension of the Kingdom of God----people converting and embracing God's rule over their lives?  To be honest (and I am open to correction), I don't think that's an overly big deal (as important as it is).  People prior to Jesus were turning to God and choosing to be ruled by God.  I just have a hard time accepting that what we basically have now----Christians living decent moral lives----was the inbreaking Kingdom of God that motivated Jesus to act.  I'd expect Jesus' mission to concern something a little more unusual, or cataclysmic.

Another point: Witherington defends the authenticity of sayings in the Gospels about the church, treating them as from the historical Jesus.  Witherington does so on the basis of their Jewish or Aramaic feel.  Witherington states that there are scholars who do not deem those sayings to be authentic to Jesus, for why would Jesus speak of the establishment of an institution if he expected for the world to end soon?  I think that's a good question to someone like me, who tends to think that Jesus regarded the end as imminent.  Witherington responds that such an objection presumes that Jesus saw the end as imminent, which Witherington does not think is necessarily true.  But Witherington also contends that, even if Jesus thought that the end was imminent, he could have still envisioned the establishment of an institution.  The Qumran community believed that the end was imminent, Witherington notes, and it established a community with institutions.