I forgot one other, important argument: You proposed, what if there was Incarnation but no Resurrection. Turn that around.
What if there was Resurrection without Incarnation? What would we have then? No Trinity, no perfect sacrifice, no "For God so loved the world..."
So, I claim, Chrisitianity would be much less, or more different, without the Incarnation than without the Resurrection.
Well, based on the axiom that God's essence cannot die, there can be no resurrection without Incarnation. But I see that as a "mechanics" argument, not one addressing what it means to Christianity itself.
But if you are supposing that a regular human came as a prophet and then was later raised from the dead, I'm not sure what that would really show. The Incarnation IS necessary for Christianity, but the Resurrection is what defines it.