Treating this more seriously, yes. Noctis doesn't have a job, he's defined by being able to do all the
other jobs (more or less); he's basically like our poster boy Midlander, switching around between jobs. If I had to classify him as an
actual canon Final Fantasy job, he'd probably be an
Onion Knight. (Or maybe a
Freelancer.)
Though, Onion Knight
would be an interesting job. Especially if you took the War of the Lions approach, where the Onion Knight job level is determined by how many other jobs you've mastered. I don't know
how you'd do it right, though.
Maybe the OKN (Onion Knight) has a level that's the average level of all your full combat jobs (including those not unlocked, and excluding any limited jobs), and in proper Onion Knight fashion is able to equip any gear you could on a given job. So if you have Gunbreaker at 78, your Onion Knight would be able to equip any Gunbreaker gear up to level 78, provided the Knight themselves was level 78. If you had MNK at 43, you could mix-and-match the GNB and MNK gear, provided the MNK gear was level 43 or less (and, obviously, that the Onion Knight's own calculated level is sufficient overall to equip whatever gear).
So if you had all the full combat jobs at 80, your OKN's level would be 80, and you could equip any level 80 (or less) combat gear in the game.
It could be really fascinating to shuffle around gear cross-job, both for substat optimization purposes (and for glamour purposes, I admit).
And it would be a neat incentive to have leveled all the combat jobs, beyond things like "You get a title!" or "You get an amaro!" or "You get a horrifyingly garish hat!" But I have no idea what sort of ability-set you'd give OKN. Can you just pull bits and pieces from other jobs? It doesn't feel like that would work. Maybe you have to define a set of abilities per-job you can pull from, and once you've got the origin job to the appropriate level
and the OKN to the appropriate level (by leveling all the jobs), you can use that ability on the OKN?
I mean, overall, OKN would be such a weird outlier I suspect it would need to be a limited job like BLU currently is, with its own challenges and subsystems.