I can't image that the producers didn't care if the lead was a man or a woman. That stuff matters to producers for ticket sales, especially back in 1979. Do you have a link to prove that none of the film maker's cared?
Just the usual trivia: John Byrne (an artist on the X-Men) based his drawings of Kitty Pryde on Sigourney Weaver and even did an X-Men comic released in 1981 where Kitty alone battles a demonic monster in a story that was an obvious homage to Alien (1979).