I have had several FOWLR tanks, and they were all mainly large agressive fish. I have had LOTS of triggers, and I love them. But, I have never had a Clown. I had an Undgelated once, but probably won't do that again. Those two are particulary nasty.
I had a Niger eat a Lion, but you may be right, I don't know if the trigger killed him or not.
It's risky keeping large and/or agressive fish, but I enjoyed it. I would try to trade fish if I saw too much agressision. One of my nastiest, and longest lived fish, was a Damsel. He beat up lots of other fish, including some triggers.