We also have a lionfish with triggers together, but chose the most "community" of the triggers (pink tail, picasso, and blue jaw). So far so good.... no nipping going on two months together now.
Really, a Picasso is safely co-habitating with a lion? I've been told by several people that they're notorious for nipping at lions. Then again, most people don't have a tank the size of an Olympic pool like you do, either... B)