You felt that too? That's cool

.. What do you think if the cape was the weapon for this job? Since you know Spawn it might be easier to imagine that than someone who's only reference is Doctor Strange (tried to reference Spawn too). Like Spawn, in part like Bayonetta, it could be really interesting "weapon" concept that I don't think you'd see as an item to equip very often in a game (especially as an MMO).
Also would ensure the brooding look of the job I think lol and an opportunity to make some wild looking relic weapon. The animations would need to be able to be designed well though, but once done I think it would work (attack animations/ability animations outside of transformations would be beyond just a simple sword swing). It could also be a key part in the animation shift into void monster like things or gameplay mechanics (auto defending cloak/growth mechanics, etc), helping animate the shift (covering parts up so it looks good from human to not).
Is Vincent's cloak actually sentient though? I don't remember reading about that, that'd be cool to know. I feel void / eldritch magic with a sentient cloak would work well together as well, and with the cloak could give the job high mobility - at least I imagine a Vincent inspired job to be very mobile.