What if Wilson wasn't in Niger to investigate, but rather to carry a message and/or warn someone?
My husband and I were puzzling this out tonight and came up with questions exactly as you put it. I've said before, I question the loyalty of a CIA agent whose spouse carries on as Wilson does. And tonight we talked about why on earth WAS he sent? And I suggested to my husband what you say--that maybe it was to meet someone, etc.
I would just add to your comments that there is evidence that someone in the CIA was interested in promoting Joe Wilson's embellished and burnished version of his trip. See the BBC story of July 9---after Wilson wrote his July 6 op-ed but before Novak's July 14 Plame citation. The BBC quotes an anonymous "CIA official" who totally promotes Wilson's story and says the WH was briefed on his Niger visit. This turned out to be false. George Tenet specifically said in his statement that the WH, VP and senior WH administration officials were not briefed about Wilson or his trip. It is not clear to me when Tenet learned of it.
So the question is, which purported "CIA official" had an interest in pushing this angle----an angle that was not based on fact?
I think the real story here is one that we probably won't ever know, and that is who is in Plame's group and what mischief they have been up to.