Does it make sense to have heterosexual characters in every game if the script calls for it?
I don't think it's a case of "tokenism". If they only add in 1 gay guy and 1 lesbian in every game, then it can come off that way. But there are between 210-700 million LGBT people on the planet (depending on the estimate that you use). It's not unreasonable to expect to see an LGBT presence in a game where it wouldn't run counter to the story (i.e. a pre-determined straight PC) in a game dynamic that sexuality plays a role. It's not contrived to have a character who is LGBT "just because" any more than it's contrived to have a character who is straight "just because".
The other issue that I have is with the interpretation that you put forward about DA2. It did have a variety of sexualities. It had straight people, bisexual people, and gay people. The game didn't only feature bisexual characters. Not even all of the romances were bisexual (20% of the romances were straight).
To me, I just find the notion that a character has to have "a reason" to be LGBT to be insulting on some levels. No one calls it tokenism or pandering when a character is straight for no good reason. I don't see why it's different for LGBT characters. And that's why I don't see any issues with including options for LGBT PCs in games with customizable PCs that aren't pre-determined. If the script would allow for it, why wouldn't you include some?
Well, yes, it does make sense for heterosexual characters to be in the story, just by virtue of most storytelling and how it is done. The tropes of it, basically. Not to mention because we are dealing with sexual pro-creation and intimacy through that. Some stories it becomes a major plot point, such as Origins with Morrigan and how you handle the Dark Ritual.
The truth of the matter is, heterosexuality can never be tokenism because it is considered the norm by a lot of people, by that virtue it is a false argument to make really. The only way that can be reversed if the whole cast is gay, and you have a heterosexual character in the mix; the complete opposite of current scenarios.
The interpretation I put forth with on Dragon Age II is how a lot of people saw it though, you may not have but thats how it is. The variety of sexualities was moot because the players sexuality was the only important thing in the game. Sebastian being straight is not usually included in the conversation of course, but for the others the major complaint was how they were undefined or implied to be one sexuality or the other.
For me I had no problem with it, as someone who is bisexual it made things easier. But I never saw Fenris as bisexual, or Merrill for that matter. Part of this was due to how the game handles dialogue and interaction, you initiate conversation and pursue the romance first for those two. Less so Isabella and Anders I agree on that, but the perception is that these characters have no sexuality. To say they are all bisexual, well, I don't even agree with that; it is really determined by how the player reacts- I romanced Fenris in my main playthrough so I considered him gay vs bisexual for me. And that rubbed people the wrong way because the characters were less defined in the end.
Silly argument in the long run I would say.
My fear is very reminiscent of affirmative action-style of characterization. You already have gay characters being scrutinized completely, and the big problem is that even with Dorian, people claimed that he was all about his sexuality that made him special (it wasn't at all, can argue that to death) which turned off people for being contrived. It's not true of course, but with that scrutiny on everything, and with a major ideological split going on in the gaming community right now, I feel like caution should be used. When they include a gay character, they need to be really careful in how its included.
Like, Ubisoft announced a transgendered character in the next Assassins Creed Syndicate. The thing is, that was the only bit they announced...nothing about the character at all. I hope that it's not a big-deal in game at all, or at the very least, its something that is mentioned a few times because of the time period they are in (19th century) and all of that, but the fact that the character was announced as transgendered and nothing else implies the focus of the character is that fact about them. That, is tokenism that I hope is avoided, for what it's worth. It was what I was worried about with Dorian and Sera when they were first announced, but thankfully there was a lot of talk about them and their characterization first, that was thrown in as an after-thought kind of deal.
Just my two cents on this I guess.