Adding all of these things without raising cost is impossible.
It can't have a LegionGo screen size and still be the same size. The screen size and lack of ergonomics due to it are the biggest drawback to the LegionGo. Shrinking the bezels would be great, as the Switch did, but it's already a bigger screen than the Switch without that.
I'm a grown-up so I don't game that much, but I really wonder who the folks are who have worn out their joysticks in a year. The device getting dirty I can kinda see, but who games enough to do that without a case? I personally think the white looks sharper in a crowded marketplace of black devices.
Another USB port would be convenient, but doesn't feel like a must. I'm not sure when I'd ever use two without being docked, making it redundant. And ports are space. Far and away the top priorities are the SD card issue (though I'll never use it with my SSD upgrade, if it exists, it needs to work reliably), and battery life. I'd rather ASUS devote every iota of space gain to a larger battery and otherwise do nothing to raise the pricepoint.