They are limited now in a way that you can't just drop someone anywhere. You select a receiver group for each side, a tight end configuration, a backfield configuration, and whether the QB is under center, 4yds back, or 7yds back. It then verifies that the formation is legal.
Extreme configurations could be justified near the goal line or in last second scenarios. Maybe I limit unusual formations to those situations.
Fun fact: The longer a formation name is, the more likely it is to not be useful.
