Of course, Odo could have been an asset, but it's a question of whether the end justifies the means. He *is* after all someone who perpetrated genocide - so is it right to use the technology that was developed in order to commit that genocide?
Technology itself is neutral.
BTW, there are Carter/Teal'c-fics out there. *g*
I've already decided Teal'c's perfect pairing is Lya.
So, these people who write such things are wrong.