Not entirely sure if this is a bug or intended but here we go...
I recruited too many weak exiles ASAP, and then couldn't find away to G-Kick them in order to free up space, my next thought was to just kill off the weaker exiles by sending them naked into battle vs late stage missions, this also didn't really kill them off but one was abducted and a new mission appeared to save them with a duration of just a couple days...
Fantastic I thought, I'm finally free of this annoying guildie. Unfortunately, even after the mission has expired and I have an open slot in the guild, I am no longer able to recruit as my "Roster is full". Thus I'm stuck with having to deny entry to even the most well rolled exiles.
EDIT: I did the mission and "let them go" and I still cannot recruit.