I'm actually a bit newer to the game, so I'm not sure as to which various activities this pertains to. All I know is that while I'm playing gambit with my friends, I get disconnected from the servers and immediately rejoin only to have my slot filled by a random person within the minute I am gone. I understand how this is a necessary aspect of gameplay for incomplete or random teams, however when I'm in a fully premade fireteam, it should allow them to "search" for a new teammate if they choose to. It would just give full teams the ability to let their friend rejoin if they are in the process of doing so.