Well, there are some legal formation that should be "illegal"...

-----ST-----
----AMC----
ML--MC--MR
----DMC----
-DC-DC-DC-
-----GK-----

I mean, teams without defensive wingbacks are the latest trend (and exploit)... which is ridiculous, almost no team in the world plays without wingbacks since the 1950's.

On the other hand if you use Argentina's 3-5-2 formation that gave them a world cup in 1986...

-----ST-----
----AMC----
ML--MC--MR
-DMC-DMC-
-DL-DC-DR-
-----GK-----

Guess what, it's "illegal", lol.

120 employees, they said.