I would find much more use for a non-gendered word for nieces and nephews as in... I'm buying gifts for my nieces and nephews. knee-shoes... nef-lets...???

Cousin/cousine is inflection rather than separate words. I see a slippery slope. Feminist cousines will feel slighted - I'm not a full cousin only a cousinette. Do we care about American/Americane? We already have a hard time with blond/blonde.
Will we soon be worrying if we can put le papier into la corbeille without properly introducing them first? (^_^)