τινα is placed between the γυναικα (or την γυναικα in Papyrus 46) and του πατρος for emphasis on the fact that it's την γυναικα that's in question.
Also, due to the fact that την γυναικα is a definite object, whereas τινα is an indefinite object would mean that the Greek speaker would have no issue with the fact that την γυναικα is first possessed by the πατρος, and not that the πατρος is in the possession of the τινα.
Also, for it to mean "certain woman", the τινα would have to come before γυναικα, rather than after (it would also be considered an adjective
, not a pronoun
There is such a thing as a "masculine nominative", but it wouldn't work for τινα in this verse, as everything in the accusative (from ωστε onward) is in explanation of everything in the nominative (Ολως ... ητις).
The first section is "There is reported ... a sexual immorality of such a kind", with everything here being in the nominative case then having their explanation of those in the accusative case "...someone has his fathers wife".
Either way, the traditional translation is perfectly fine (woodenly it would be "so that the wife someone of his father he has" = "so that someone has his father's wife", which one is to assume is the persons step-mother, rather than his birth mother, as it would be a lot easier to state "someone has married their own mother!" compared to what is seen in 1 cor 5:1
), and your two alternative translations are very unlikely, I'm afraid =/