While I was drifting off to sleep last night, I found myself still thinking about this, and came up with a more-or-less allegorical explanation:
Judas didn't turn Jesus in because he was that interested in a couple silver coins. He did so because he thought Jesus, as the Messiah, would be able to beat whatever they threw his way. He handed Jesus over to the Romans because he wanted to see the Kingdom come to Earth to save Jesus. In sum, he was getting restless, and wanted to set whatever movement Jesus had cooking up into high-gear.
Jesus accepting his execution, then, is more of a lesson for us than a sacrifice. It's what tells us, sure, "we can have a better world if we follow Christ's teachings" but God is NOT going to give it to us for free, and especially not to save himself, aka Jesus. It is something that we all have to work for, not something that can just "happen" because we've killed our Spiritual Leader and now expect God, in light of that fact, to realize that humanity "can't do it" by itself and hold our hands the rest of the way up. That would go against what the New Testament God has to offer us against the vengeful Old Testament system: that us people aren't perfect, but we're good enough, and if you give us what we need to be better and the chance to do it on our own, after some amount of time we will.
::prepares to be bulldozed by the boards' many theologians::