Monberaux is a Trust in FFXI? That's news to me! (Goddess I've been out of that game too long! ). I do remember though in Campaign battles in FFXI each force would have combat medics among their fighters, they'd often have names like "woundpatcher" but were mechanically WHMs despite looking like chemists, but it seems in this case as you said he really does use Chemist style abilities making him one in all but name.

I guess then, as long as the actual Chemist name is not used and a hypothetical chemist class here in FFXIV is given some other fitting name (like 'apothocerian') as the name chemist is too close to the pre-existing Disciple of the Hand class Alchemist (ALC), it could potentially fit in hindsight. Whether SE ever would though is another thing.