I don't think Vann is slow. I don't know about unimaginative. When he was talking on Greta last night (Greta wasn't there - a non-lawyer, Martha, sat in for her) he was trying to answer Martha's question by explaining the mechanisms in their criminal procedure by which the current motions as to the line-up, the DNA debacle and the motion to preclude Mangum from identifying the suspects in court would lead to the unraveling of the case - die of its own lack of substantive evidence, and that a judge cannot just fismiss the case on a simple motion to dismiss. He was trying to give a legal explanation to her answer, but she wasn't getting it at all. Her follow-up questions made that clear. There was no context in which he would have had an opportunity to go on about what the judge or the defense could further do creatively to dump the case because he wasn't asked an open question. It was a technical question that Martha asked (even though she probably didn't realize it was a technical question).
Anyway, Vann said he just cannot imagine that the judge won't throw out the line-up identification and it's quite possible he won't allow the in-court identification. If that happens, he said, Nifong would have to dismiss. Vann also said that it isn't likely the judge would remove Nifong from the case, and that doesn't surprise me, given NC's prosecutorial structure established by law.
I think it's inaccurate to consider him slow or that he's not seeing what Liefong is doing. Rather, he's reflecting what's possible or not under NC criminal procedure law which, as I've said before, is a scary thing in itself and often incomprehensible by other standards we see in other states. He also explains how NC courts have handled matters at issue in this case in the past.