Just looked it up and the entire first page of searches is about how ‘guys’ is masculine and insensitive to women. I disagree. I think the masculinization of the term is like an unneeded extra filter placed over ‘guy’ but the term itself is innocent. Guy Fawkes was a real person. He did something that caused him to be a symbol of the common person. There is nothing gendered about that. It’s the patriarchal culture that then assumed ‘common person’ refers to males. When I think of Guy Fawkes, it is his actions, not what’s in his pants, that is important. So, while there are many needlessly sexist and sexual phrases in English, I do not view ''Guy" as one of them and, instead, view it as a victim of the patriarchy just like you and me. It isn’t an inappropriate phrase to change or remove, it’s one to reclaim for all people; which is exactly in the spirit of the symbol of who Guy Fawkes is.
I think it’s pretty genderless, just because I’ve heard enough women use it about women or mixed groups. You can always use his surname instead, just update a bit to modern pronounciation, call everyone: Fuck, Fucks, Fuckers. I think that solves it.
Calling everyone “homo” is another good one.
Some languages like French use “ils” for mixed groups (same as male groups). But others like German use “sie” (same as “she/her”). Plurals in german, I think, usually become feminine (die Manner) - although German has many other gender-bending cases that I can’t begin to understand. I’m sure there’s lots of other languages that have a million other features/inconsistencies/expressions of patriarchal domination like this.