Even though I share many of the points you made, I think that there are a few others things to consider.
First, it seems to that you may have slightly blown out of proportion the argument currently made by some critics about diversity in games for the sake of clarity of your own thesis. I don’t think that even among the people who criticize the lack of diversity in games, most want every game to be diverse, want quotas, or any kind of mandatory measures on anything. But, I think that some of the major publishers may get a bit too complacent as far as main characters are concerned in some games. For exemple, making the main character a typical american young man in his mid-20s or in his 30s seems sometimes way off and just a plain surrender to the marketing department. But only sometimes : characters like Sam Fisher, JC Denton, Eddie Riggs or Geralt of Rivia are great the way they are. But when you get into the skin of the main character of Far Cry 3, it seems forced and not very interesting since the character was designed to mimic the average american hardcore gamer. All too often, some companies who lack time or imagination to develop interesting characters will resort to the default one who is a young white male. This “default” character has several flows : most of the time, he isn’t interesting at all and we see him way too much in too many games where other choices could have been made. So much that it becomes boring. In this regard, I think that Valve did a great job in this area with the Left 4 Dead series in which there was a form of diversity among the characters that was mimicking what really existed in the US.
Second, I think that for Tauriq Moosa’s argument to be fully understood (since he was the one who made it about The Witcher), one has to look at his cultural background and at the society he lives in. He comes from a diverse society but where a fierce form of racism still exists (at least according to people I know who travelled there). He comes from a place where ethnical diversity is very high and where it has been that way for a really long time. And I am not surprised to see his ideas resonating in the United States, a country which also enjoys a high level of diversity. So, in an irrational, unthought way, it may just come as strange to him to see games with no ethnical diversity, since he wasn’t born in a place with high uniformity. By applying the political and cultural mindset of countries he knows, he may find strange (the lack of diversity in a game) something that is a non-issue in some countries.
Third, I think that behind this argument on people of color in games, the real debate, the interesting discussion is the lack of cultural diversity of most games. Titles like S.T.A.L.K.E.R., The Witcher, Metro or even german management games are interesting because, as you said, they reflect the specific culture in which they were made. And today, a lot of games don’t do that and go the easy way, using tropes and clichés to try to appeal to the entire population of teenagers in western countries. Today, Ubisoft, the biggest french video game company, creates games that could almost be made by any american publisher. The specific culture of France (or of Quebec) doesn’t get anywhere into the game. By trying to be familiar to the entire western markets, some games forget that what we crave is the unfamiliar, the new. This is probably the biggest problem with the game industry right now : not its reluctance to include diversity for the sake of it in games, but its reluctance to venture outside established conventions, to treat games as art and to make diverse experiences.