Rescue isn't that hard, if you throw a few Dragons behind you before you go through the hole (because some guards usually come from behind and run into the Dragons). And the rest of the guards can be killed with explosives, so no aimed headshots are neaded. So not that hard.
Escape and Defense are really hard, because both levels have a hard part at the end, where unlimited (?) guards follow you.
And yes, theoretically only Attack Ship is left. But maybe the only existing Villa dltk vid was done in slow-motion, so we couldn't really count it as done. But I already tried it and Villa is possible with some patience.
But for Attack Ship I see now way to complete it. Without explosives you need 40 shots (2 clips) of your Mauler to kill a Skedar on dltk. And even running around the Skedars wouldn't work, because they would kill Elvis, if you don't kill them.