I figured we were working on the assumption that we do want to try him, since otherwise the question about whether he would be Mirandized is rather pointless. (Unless the question "Will we try him at all?" is implicit in the original question)

If you don't think he deserves a trial, and that it's OK to just kill a suspected criminal on the basis of "evidence" that nobody outside the Pentagon and the White House, never mind a judge or a jury, has ever seen, then sure, he's fair game. I've never thought that the Geneva Convention applied to terrorists. I do, however, believe that international human rights law does.