Chemist is a mage by default, so I can't see it getting any light armor beyond what a GEO/BRD could get (though Ayanmo +2 would be cool area to start). Healer/debuffer would be an interesting mix.
Guns/Knives fits the lore, and you could just skip the crossbow aspect and give them status effect bullets specifically for them. Or abilities/items that alter their marksmanship prowess (Balk, Mustadio from FFT). Would be cool to have a backline healer job that can not only support the party defensively, but provide debuff support from afar (the range of a gun).
Wishful thinking.