actually, i think sonon not being controllable suits the perspective of yuffie. sonon kind of pretends/allows yuffie to be his "boss", like he's her older brother, right? when yuffie drops in battle he gives the remaining amount of his HP to her, and then he obviously permanently does that at the end of the DLC. you spend the whole DLC in the perspective of cocky naive yuffie that the one actual adult character should feel out of reach. idk, I just felt like it worked well in terms of its narrative structure! nero is still incredibly stupid and should've been scrubbed from the whole thing, and these dungeons are kind of too big, but idk, i had a good time :)