I have a few ideas. A good first step is simply to have more empowered female characters, and have them be actual characters. Not something like "personality trait: 'is female'", real characters who just happen to be female. Have more empowered female protagonists who aren't traditionally attractive, because
there really is basically ****-all in that realm, and it sends a message that if you aren't eye candy, you aren't wanted. Stop treating "attractive white male" as the default setting for your game's protagonist, to the point where if your protagonist isn't white and male, it's something to apparently write home about.
Kick these *******s right the **** out of the industry; they are a big part of the problem.
But honestly, all of these are just not enough. This is a really hard problem to solve, for a variety of reasons, not the least of which being
the dismissive attitude those within the industry have towards female game devs and gamers, regardless of competence. Or, to put it another way, if you meet someone with a female Mii avatar online, and they kick your ***, what's your first assumption? "This is a woman who's really good at smash" or "This is a dude with a female avatar who's really good at smash"? The fact that for most people, it's the latter, is
part of the problem. I don't have a solution. I have ideas - stop shaming women for speaking up about these issues, stop pretending there isn't an issue, etc. - but it's hard enough to convince most people that the problem is even real, even after a feminist game critic got
bomb threats when she accepted a speaking gig at a university, so solving it... Well, I do my part to call out obnoxious sexist behavior.