That doesn't really work in German as the pronoun "sie" changes meaning depending on context. It can mean "she": Sie ist kalt (she is cold). It can mean the plural "they": Sie sind kalt (they are cold). And it can be used for the formal "you": Kommen sie? (are you coming?)
But isn't that what we're talking about here? "They are cold" can be plural in English, but it can also reference a singular "they". The formal usage would just go away with use probably, or stay around totally on context.
Seems like "sie" would work just as well in German as in English.
