The problem I see with military tribunals with sealing sensitive info, is that the political operatives will use it against the current administration. They will start crying "they are keeping information from us. What are they trying to hide? Why is this administration so secretive? blah...blah...blah."
While the idea is a good one, there is no way the media, opponents of the military in general, political operatives, etc will allow it to happen. Any time you announce that person X was tried and convicted and you refuse to release the information that convicted them, you are opening yourself up for cries of "Foul!" There is no way, IMO, it would work in our current political climate and the Hot Pockets mentality bred by the media.