"Eine Institution wie Guantanamo kann und darf auf Dauer so nicht existieren."
Thus, I make the translation to be:
"An institution like Guantanamo can and should not exist in the longer term in this [or: its present] form."
Some people might use "so" as a filler in spoken German. But in Germany, it is customary for print media to submit interview transcripts to the interviewees prior to publication. If this meaning wasn't intended the Chancellory would presumably have requested that this be amended.
Merkel is trying to be critical without being categorical, methinks. The fact is that what we're experiencing right now is a top-down disaster. -Paul Krugman
However, I don't think the ommission of that one word is sooo important. I think Gitmo is more an icon than a specific place. Therefore: Gitmo "in a different form" would not be Gitmo as we know it.
Do you know what I mean? Atlantic Review - A press digest on transatlantic affairs edited by three German Fulbright Alumni