I fully support the playersexuality concept. I don't favor the 2/2/2 configuration to playersexuality. If there were six, or twelve, or twenty love interests, I'd still rather the playersexuality system was used. I have a really hard time relating to people that feel this system somehow diminishes the characters.
With playersexuality, ideally, you're not "changing" the NPC's sexuality. What happens is that you boot up the game with a blank, imaginary reality. Your choices in character creation shape what that reality will be around certain skeletal outlines that never change. The NPCs aren't existing people, they're skeletal concepts that will be altered slightly based on the reality you create. This is exactly the same idea as what you're doing with the player character. You choose their gender and appearance. You even make the choice as to what background Shepherd has, as well as the race and background of the Warden and the Inquisitor. Throughout the game, you make branching decisions that set your reality apart from other possible realities. Certain people may or may not be dead, they may or may not be important leaders vs town drunks, or otherwise. You influence major decisions they make and, in some cases, make minor impacts on their overall personality and their slant on some future decisions. A major aspect of Bioware's games, also one of their major selling points, is that you're offered the chance to have your choices shape an imaginary reality.
I've seen arguments that, "well, the player character is me, I control them". The fact is, no, you really don't. You don't really ultimately control the player character. You have a much wider net of control over them, that doesn't mean you have full control. The choices you can make are still reined in by plot constraints. You're still limited to a handful of personality traits, none of which may strongly line up with your own. You're still left with a limited amount of rational expressed for each decision, also which may not line up with your own opinion. You still have to make only decisions that wont completely derail the plot, whether this is what you'd actually do in the situation or not. You're influencing one of a selection of skeletal concepts offered for the given reality towards a set end goal.
So, what is the reason that we can't make all of these decisions for the whole party? The answer seems obvious to me. The party characters are used as a way to offer multiple outside opinions that balance the world views you're dealing with. A side element of playing the game is managing their disagreement to a point where you either have to give or give up a party member, through them leaving or having to be killed. The characters beliefs remaining semi-static is an important part of fleshing out the plot and tone of the game. While things like the "harden" feature in Origins, or the few times you are able to reasonably talk down party members on issues, don't drastically change that, because their general personality and slants remain intact. Completely changing their belief sets and alignments would have a huge impact on the plot.
However, the party character sexuality has absolutely none of this impact. I haven't seen anyone in this thread actually argue that a heterosexual, bisexual and homosexual character can't all be of equal quality. If this change isn't inherently of lesser quality, if one sexuality isn't inherently superior, how does the change diminish the story or the character? In Thedas, and also in Mass Effect, sexuality is presented as nearly a non-issue. We've never seen anyone face even minor harships for their sexuality. While there's a plethora of discrimination related to race, religion, nationality, political alignment and various other attributes, we've seen nothing like this concerning sexuality. Thus, I see no reason why sexuality is integral to the plot or the need for immutable party character attributes. There is no reason for their sexuality to affect their personality, political beliefs or alignments. There's no real need for another instance like Anders and Karl being represented differently for males and females. It's very easy for some characters to simply be presented as bisexual in relatiosnhip history and some left ambiguous, like Merrill and Fenris, while leaving them open to everyone. We don't need to throw the baby out with the bathwater on this. It's an easily fixed issue. Sexuality itself is a non-issue that, when altered, simply allows everyone access to the side content they most prefer.
And, I just can't understand, why is that a bad thing? It's not that I don't care if "getting my way" harms story quality. It's that, in this specific instance, I can't see the give and take. I'm paying $60 for this game, why shouldn't I have the ability to access the content in a way that's actually enjoyable to me when there's no major change to the story in making that happen? Telling people to simply pick another gender is NOT an answer. Entering into a heterosexual or homosexual relationship as someone of the opposite orientation does not have the same appeal for many, many people. Many people would rather "settle" for the available option than replay as the opposite gender. I just cannot relate to the idea of wanting whole sections of the game restricted for basically no gain. There's no realistic way I've seen argued that playersexuality either diminishes the characters OR the plot, so it seems to me as if this is just restriction for restriction's sake. I'm not saying never have restrictions. I can absolutely understand a pro-templar love interest rejecting someone that acted in-game like another Anders or Adrian. This makes absolute sense with the plot and makes the world and characters more believable. Having them toss their beliefs aside with little to no rational explanation for the change of heart absolutely does diminish the character, to me, which is why I never partook in "rivalmances" in DA2. However, I see none of this represented in playersexuality. I can't, as much as I try, relate to the vitriol against it. This is especially so when I see much more glaring issues with "playersexuality" in relation to things like beliefs, rather than gender.
tl;dr version--
If you want restrictions, lets focus on restrictions that actually DO effect the character and story integrity, like choices relating to their beliefs and alignments. Sexuality is irrelevant to the actual character develop, or the integrity of the narrative. The entire process of a Bioware game is taking an active role in shaping an imaginary reality, constrained only by elements that keep the story on track. Sexuality has none of the earmarks of being one of these elements.