In Quenya the general plural performs the functions of the Sindarin group/class plural, cf. Eldar -- Eledhrim, elenion (ancalima) -- (aglar) elenath.
I guess this is true for any language without a proper class plural, but Quenya also has a sort of collective formation Eldalie. In German and Russian, for example, 'news' is formed via a collective/abstract suffix (Neuigkeit, новость), thus literally indeed 'newness, recency', and is distinguished from just some unspecific 'new ones', although one probably will find a number of languages where it is indeed the plural of the adjective 'new'. Anyway, it's just an idea.