Not all of them are tameable, if you have Feraldo he can be tameable in future updates. Skru'Vaks on the other hand, not so, and a lot of them are tops and demanding. But on the game side. Rylan, Bradley, Feraldo, Cicero, and Zyron are the best bet for battle. Although some of them cannot climb with you in Akra's second floor, Rylan,Phoenix, Cicero specifically because they are poor.
I hate Chip's (Ship's AI) uniqueness in battle- he has robust defense yet cannot be healed by pills and other medication because he is an android, I hope he had a self-repair ability in the future update. Its annoying and time-wasting go to and fro in the ship just to repair the android.
And also they should segregate (main utilitarians from warriors, so they can space more character utilizing the ships capacity for crews.)
Cause a lot of characters are useless after they were taken as a crew (and exceeds their usefulness (i.e. main missions), example. (Hakkan, Skru'Vaks, Levi, Master X, Asmodeo).