Kujata is already in FFXIV - he's just a regular bison mob that shows up as the overarching antagonist of the MRD class quests that is terrorizing La Noscea (the level 30 MRD class fight specifically requires you to finally kill it for good). So yeah, it's just a regular monster.

And Ark is also in the game already too, as 'Cruise Chaser' (which was a clever reference to FFIX-Ark's original design origin - it was based on a mech from an ancient Square game on the PC called Cruise Chaser Blassty (in FFXIV Ark shows up as a boss in Alexander-Midas ~ Heart of the Creator, thus linking it with a Primal already (but not specifically a Primal itself).

And I don't see Ragnarok appearing as a Primal, on account of the Allagan Empire Internment Hulks are actually starships of the Ragnarok-class (referencing FFVIII's airship of the same name). Not to mention the weapon shows up in FFXIV as a relic weapon too (the relic weapon zeta great axe for WAR). All the other choices are possible though.