Honestly, tapping on the summoner bit, if we could summon the full size primals to our aid for extended periods of time the majority of raid bosses would get covered up by primals.

Like seriously, can you imagine Brute Justice being punched by 4 full size Titans that are clipping through each other? You would not even be able to see to click on the boss.

Sure it would feel more Final Fantasy (specifically, Final Fantasy XII) but it would be at a detriment to gameplay.

I also feel that in some ways the classes we do get should not function too closely to how they are implemented in other final fantasy games, but still keep within the theme. That way they feel a bit more unique here instead of just being carbon copied from another FF game. After all, this world is treated as its own. So similar classes could have gone an entirely different route compared to other FF worlds. The Ninja in this game being more of an assassin, instead of an evasive distraction that alters the enemy's def.