Kurt can help with the sneaking. He's a teleporter with shadow-camouflage, after all. And on that note, we have a teleporter for the extraction mission, so that's awesome. He can take a few passengers, so getting fellow rescuers moved around as well as jailbreaks are simplified a lot (though he has a puff of smoke and a sound effect, and he's not invisible, just hard to see, so this still calls for finesse).

One disadvantage is that if you see him properly he's kind of... memorable, so probably shouldn't go on any parts of the mission that depend on rolling charisma rather than a physical stat. And he's not a heavy-hitter should it come to combat, though he can be quite effective if there's room to port around and antagonize bad guys.