They'll wreck armor stacking strats, that's for sure.
I'm still working on the position control part. Pit Trap is so expensive and Quicksand too unreliable, caltrops alone insufficient, and the book doesn't have a lot of room for out of school pushes or vines or force hold. Goblin slingers have a lord that helps, but Greatbow wants to fly, maybe?
I'll be very interested to see what you come up with.