I think MMOs are an interesting setting, but they do remove tension and it's very difficult to get it back without resorting to the good old 'die in the game you die for real' trope.
One thing I would really like to see is a show where the story in-game is important because the people in the show commit to the in-game story. Like, it's not because they're forced to like it, or because they're being threatened or whatever; it's because they're playing a game and they want to have a good time with the game. Maybe some kind of RP thing, I don't know.
That or an e-sports tournie I guess.
How about an anime about LARPers? Not stylized or anything just some dudes with beards wacking wooden swords in the forest.
I think for an MMO show to work it really has to focus on the characters. And then I'd probably rather see their outside lives than inside. But SAO can't do anything like that because Kirito has the personality of a bar magnet and every other character has the personality of lead filings.