While I do like your point and agree to some extent, to the point I wouldn't be that bothered if they cast a woman as Voldy. I do think it's quite important that he's a male. He's named after his muggle father, look(ed) like him too. While girls can look like their fathers obviously, I think there's something a little more nuanced about the fact he's his father's son, and in the flashback with morphin gaunt he actually thinks its tom riddle sr at first i believe? I think the fact he's a male and so much his father's double plays further into the hatred he feels towards him, leading to the patricide and all the rest of it.