Yea IMO you would still have a nipping problem in the long run. While juv. they should get along well. On the naso start small but your still dealing with a short tank and these guys need swim room.
I'm thinking of dropping the lionfish altogether- and getting either a dogface or porcupine puffer- or both- Then maybe a trigger, tang, wrasse, angel. IDK yet but would both dogface and porcupine do fine in a 120g with a trigger?
I think, though I dont have any experience, that most people recomend much larger than a 120 for a porc puffer, since they get well over 12" long, closer to 16" I think.
personally, I'd want to keep a big wrasse, an angel, an eel and maybe a puffer.