Garlean Playable Race (?)

[Enkidoh]

There's nothing stopping a Duskwight from doing those things; it's just that people don't tend to like them much while they're doing it. (Though Kan-E seems like the "judge on individual merit" sort anyway.) The lancer questline revolves around a Duskwight who used to be a member of the Wood Wailers and we've seen at least one current Duskwight member of the Twin Adders.

^This. Also, the main reason why Duskwight are ostracized so much is due to the backstory of Gridania's founding - when the elementals granted the elezen of Gelmorra permission to settle on the surface in the forest, a renegade political faction refused to comply, perferring to stay in the underground caves and abandoned subterranian Gelmorran structures rather than cowtow to the fickle whims of the elementals, and it was this troglodytic group that eventually became the duskwight clan, becoming physically distinct from the main 'wildwood' elezen of Gridania. Duskwights are welcome in Gridania, they just have to be prepared to follow Gridania's laws (namely, the will of the elementals), which, naturally, many refuse to (especially to do with illegal poaching), which then drives them to the fringes of society, becoming bandits and outlaws.

There hence is nothing lore wise stopping a duskwight from becoming an adventurer, unlike a Garlean which would require a far greater stretching of the lore for credibility's sake. It even makes perfect sense that duskwight become adventurers specifically given the clan's rebellious tendencies fitting right in with the free-spirited, mercenary nature of the life of an adventurer. Garleans are just too buttoned-down and staid for such a life, which is pretty telling that Garleans who are rebellious eventually end up defecting to Eorzea anyway.