Here we go again. Time for the copy-paste reply:
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Largos are out as, according to the personal story, they are incredibly rare and avoid contact with all other races if at all possible. It would be as stupid as the Miqo’te in FF14 ARR – they’re supposedly rare and solitary creatures yet the designers make them in such a way that EVERYONE who faps to nekomimi will roll one.
Largos avoid land-dweller, but they aren’t necessarily rare. If the deep sea dragon appears, they could play an important role.
An advantage of the largos is their human-like body structure, amor skins that look good on humans/norn/sylvari will also look good on largos. (most likely)
Animal themed races like tengu, centaur, dredge or hylek would have difficulties with this subject. The charr are a good example here (as you already mentioned).
An other advantage is the mystery, we know very little about this race, so there is (maybe) much to discover.
besides i don’t know any mmo with playable aquatic races, therefore the largos can be an interesting choice.
as for myself i would like to see Largos as a playable race. 