There's always a risk with multiple clowns. I sgree that two different complexes would be easier, but with the right conditions, I think you could get away with it. I would only try it if your tank has lots of structure, and all the clowns were about the same size, and introduced at/near the same time.
Honestly, I think that if you put 4 clowns in a 1000 gallon tank, but it only had one rock in it, they would probably fight like crazy for that single rock.
Even with favorable conditions, I wouldn't expect that you will get the pairings to go the way you want them to. You might well have Mocha/picasso and snowflake/picasso.
One other note. I would stick with tank bred fish only. Just my 2 cents