The problem is also it isn't shown whether the capacity is full or not, No one's telling me how many can actually join in or if there's a limit. Regardless, a lot of the early-mid crew members are disposable (killable) and/or you can reject them. SPOILER do not read if you don't want some details: Some should build their enmity to actually able to reject them just like Rylan's case. Katari also can help at the ship without inviting him in, some crews are skippable such as Hakkan (Sub'Guh-Nir Alpha), (Skru-Vaks are mission oriented yet you cn skip them if you fight the boss in Sithyrya). Permanent crews are Arthur and Sam (which is directed by the main missions). Time-limit Recruit would be Cicero and Alaster (cause they disappear if you don't get them sooner to the ship). Some crew were actually limited to set foot on the ship such as Garth (temporary), others are below level treatment like Master X(crew's slut/former owner of TSB). Difficult to get crews is the owner of Papito's Toy XXX (The only character who had full name tag in the rooster) Isaac (The Captain that preeceeded by You) and Levi (The victim of the TSB (The Silky Blindfold).
The names spoken above were the only known recruitable members I know of.