I'm not sure BT quite fits the profile you're aiming at, Wolf, though I agree that they exist

For one thing, her lack of a social life, for me, suggests the opposite of a player screaming for attention. Her melancholy and proclivity to drink suggest to me that she really is using the game as another form of pure escapism rather than as a dating accessory. The class reunion comment is particularly telling, as these are the occasions when people like to brag about their accomplishments - which is precisely what would motivate an escapist tendency. The fact that she is still a newbie in terms of game advancement could simply be a lack of engagement with the mechanical side of gaming, which can occur with anyone (particularly those who 'play for fun', lol).
Bear, on the other hand, is, I would suggest, far from escapist. He seems to comment very frankly on his failings and actually uses the game as a chance to face and (at least partly) conquer them, rather than run away. His relationship to Tsukasa, and indeed, to Subaru, takes particular courage and the game becomes an element of great growth for him. I would say Bear, despite his real life troubles, is one of the more encouraging examples of a 'mature' gamer.
Mimiru and Crim are probably the closest to the mainstream gamer - young, have relatively normal lives, don't take themselves too seriously, and don't like to think too hard.
Subaru is probably the most interesting case, if noirlax has the time/inclination it would be nice if he could develop that analysis somewhat ^^ For me she doesn't quite fit the stereotype of the disabled gamer, who in my experience tend to be highly mechanical and not as social in their approach to gaming. At least in English society, having a disability rarely if ever forces people to seek virtual friendships, but it can spur them to make powerful characters. But perhaps a Japanese or north Asian attitude to disabilities, or to gaming, is a difference-maker here.