It really wouldn’t be a bad idea for the event squads, as well as the premium ones, to have their own extra slot, this with the aim of balancing those who play Free to play a little with the premium players.
While premium players can have up to 11 squads, the rest of us players only have 4 spaces, and although it is not pay to win as such, sometimes it becomes a considerable advantage and even more so when a team hosts 2 or 3 premium players and therefore I firmly believe that an additional slot exclusively for event squads is a very reasonable idea.