I think could start with a base class of tamer have it use whips. Base ability would be capture which you could only use when the mob is at like 1/5th hp something along those lines. Now as a tamer the pets would pretty much just be auto attack dps and no big mobs. Then comes level 30 where you can get beastmaster or blue mage. As a beastmaster your first ability would change how capture works so that it nows works if the mob is at 50% hp and it works on bigger mobs such as adamantoises. Getting abilities to increase pet damage and make the pet do its special moves. Then we would have Blue mage which when u unlock changes the capture ability into learn, you would use this ability at the start of a fight and if the mob used the ability during the fight you would learn it switching to this job could change traits from ability to capture specific mobs into the ability to learn spells from those mobs. Blue mage could even be a tank class and its big 4 spells could be from job quests.