Jeff:
I know people throw the term “smurf” around a lot, but the strictest definition of the word is what OP is describing: someone who is actively manipulating their rank so they can play against lower-ranked opponents.
I have to imagine this sort of behavior sticks out like a sore thumb and is easily identifiable. Even so, I’d still report a group like that which is blatantly advertising itself as a derank/smurf group.