A5e seems to be much better about versatility, but there doesn't seem to be a way to support subclasses. For instance, if I wanted to play an Eldritch Knight, I'd have to multiclass between Fighter and Wizard and, while there are synergy feats for this, it seems like I'd still end up with...
I honestly didn't think to directly link. I mean there's the Adze, Aswang, Azeman, Bhuta, Chorti, Chupacabra, Langsuir, Obayifo, Penanggalan, Tikoloshe, and Yara Ma Yha Who among many others.
Could you include quirks from other cultures such as counting small objects (counting grains of rice, for instance)? Have you considered how they might work as PCs if someone wants? Are you considering talking animals? Have you ever heard of the Skin Deep comic? It has an interesting portrayal...
Personally, I do not think there's much they can do to get people back. After what they did to the Forgotten Realms, I think it's pretty clear they'd rather destroy all that came before than ask what their players actually want.