It doesn't really matter about numbers, unless 'policjant' can be used to refer to a female police officer as well. If it can, please let me know as this might help in the future! As far as the English translation is concerned, either a gendered noun is required for both (in order to indicate understanding of the gendered Polish noun), or a non-gendered noun should be acceptable for both. So on that note, thanks for the addition :)
Polish generally goes rather the other way than English - for many names of professions which used to have only one (grammatically masculine) name, feminine versions are being created. Some of them enter the language easily, some not.
On the other hand, it is possible that a profession has a (widely accepted) feminine variant of the name, but a woman can also use a masculine version. This would then be just a matter of personal preference, although I believe that using the feminine version is still a lot more common. Anyway, we recently wondered about that, and divided the list of professions we teach into those where we think that using a masculine version by a woman is possible, and those where it just seems too strange. We think we were quite lenient with this list. "policjant" is on the second side of the list, the 'too strange' ones.