Hello! Far be it from me to claim to be able to read Greek, but I can at least answer this question. The ending of the noun is what usually gives the word it's unique quality, plurality being one of them. (There are a few different forms of 'gyne' that are plural.)
In the example given (1COR4:2) the actual word as it appears in the text is 'gunAIKA', which is the accusative singular form of the word gune.
The plural from of the accusative sense of the word would be spelled 'gunAIKAS'
Therefore
Are there places in the New Testament where the word gyne has been translated in the singular where it could have just as easily been translated in the plural?
Not really. Greek is an exceedingly specific language, and will tell you whether singular or plural is in view just about every time. I certainly don't know of any instances of vagueries regarding purality vs singularity. There are sometimes difficulties telling what tense of the word you are using but number seems pretty cut and dried.
Buuuuuuuuuuut:
It is that incredible level of specificity that actually gives us polygamy in this very verse. The words translated 'his own' and 'her own' are two completely distinct words. The man 'has' his woman in the sense of the way a man has a possession that he can have multiple of. (heautos).
The woman 'has' her husband in the manner that someone can have something that it is only right that they have one of. (idios).
This is loosely adhered to with only a few variations in scripture; but when you narrow that search down to human relationships; it is very tightly adhered to with no exceptions.
THIS IS A GOOD THING
Because if the singular/plural was ambiguous: It would leave it open for the woman to have multiple husbands
Because if gunaika was actually plural: it would be a COMMANDMENT for polygamy, which does not fit well with the rest of scripture
Therefore the way it is written very precisely paints a picture of men who need marriage, must get married... PERHAPS to multiple women; but a woman who needs marriage must get married ONLY to one man who will be her proper husband.
I hope this helps.