Any fits that meet our requirements are placed in the wl until a spot in that squad opens up. If you have a Rattle and a Mach in the DPS + Sniper lists, the one that comes up first will be requested. If you have both on the list at the time of forming, the FC will more than likely opt for the better ship if theres a choice.
Important to note, within WTM all fleet positions (Barring fleet need for logis) are filled on a first come first served basis. No favouritism is given to optimal fits over starter/non optimal ships.