I assume it could be implemented so that a pilot can enable a setting indicating they are willing to join fleets with friendly fire. By default, this setting would be “no friendly fire.”
If a pilot switches this setting while in a friendly-fire fleet, or leaves such a fleet on their own (but not if they are kicked), they are removed from the fleet and receive a 30-second suspect timer.
This way, a participant won’t be able to exploit their former fleetmates.
It should not be possible to switch an existing fleet into friendly-fire mode—it must be created as a friendly-fire fleet from the start. This setting should persist when fleet command is transferred to another pilot.
This prevents recruiting unsuspecting pilots into a fleet and then switching it into friendly-fire mode afterward.
In the interface, a pilot would see both friendly-fire and non-friendly-fire fleets. If their settings specify that they only allow joining non-friendly-fire fleets, they would be prevented from joining a friendly-fire fleet. If they change the setting and attempt to join such a fleet, they would receive a warning about the potential consequences.