Female Genos could be developed with a more empathetic side. Since she is a cyborg, she could struggle with understanding human emotions more deeply. Maybe she starts to learn about love and friendship in a different way compared to male Genos. For example, she might be more sensitive to the feelings of other female characters around her.
It depends on various factors. In the fanfiction community, some might find it an interesting and creative exploration of characters, but others may object due to the negative connotations of cheating. However, as long as it adheres to the general rules and ethics of the fanfiction platform, such as not promoting harmful or unethical behavior in a glorifying way, it could be considered acceptable in the realm of creative writing.
Genos is still kicking in the One Punch Man manga. The author has managed to keep him in the storyline without killing him off. There's always the possibility in the future, but for now, he's alive and fighting.