Except that you can only have as many wraithlord Troop squads as you do wraithguard squads. So you can max get 3 wraithlords as Troops and another 3 as Heavy support. However, if you were ever to do this, no one would play you. That and you'll give Iyanden a bad name. I play Iyanden and I've never fielded more than 2!
Josh