I come from a place in the Internet most people deem to be horrible in every single way. While I generally don't agree with most of the stuff said in that website, I can provide some insight on what happens around there when a pro-LGBT game is released.
- A small but very vocal group of (probable) trolls will complain about it, no matter the way they are depicted, under the argument that it's "degenerate", "pozzed" and a thousand other descriptors usually containing the word "cuck" in them. They swear they won't ever buy the game because of these small details, and will generally attempt to derail any serious discussion about the game, but they are a really tiny percentage of the population that just happens to invade any threads made about games like these.
- Some users, the less sarcastical version of the above, will automatically qualify whether it's cute or "degenerate" exclusively depending on whether the game was made in Japan or not. It's as dumb as arbitrary, but they are somewhat grounded in reality considering the vast majority of Japanese depictions of LGBT people is very different from the vast majority of their western counterparts.
- Some users will only care about whether the girls and the relationship are cute and whether it comes of as preachy or not.
- Some users will only care about whether the game presents this plot point as preachy or very "in your face". Probably the biggest demographic around these places.
Some research on Gamergate and its slow declive into the alt-right should give some light on the above positions, but the general idea is, they are tired of games being marketed on their "progressiveness", which usually tends to overinflate their scores in game journalism sites even though the games are not that good (in the case of Gone Home, some people don't even consider it a game, yet it managed to score a 10/10 in many reviews, which didn't sit well with many gamers). This resulted in an influx of games with progressive values being thrown in your face in the most preachy and obnoxious way possible just to achieve "brownie points" in attempts to replicate the success of previous games who did this, something they didn't like because it went against their beliefs and political stances. This may seem inmature, but nobody likes to feel like the games they are playing are going directly against them, so it is kind of logical to expect such an outcome.
Thing is, these gamers are very wary of these topics because they feel "stiff" and "fake", as in, so shoehorned it becomes obvious the devs are trying to virtue signal in hopes their game gets noticed by the games journalism crowd. Most of the LGBT character depictions shown on many recent games seem to default to the "accepted" representations of their gender or sexuality (how many characters would describe "strong independent lesbian woman who needs no man, is snarky towards everyone, always looks angry and has short hair", despite that description being very specific?), so many of these characters end up having the same personalities, same background and sometimes even same questlines, which to these people smells like mass produced token LGBT. The queer characters are often presented as borderline Mary Sue saints who could do no wrong, but are always wronged by (most of the time, and I think this is your game's case as well) white cishet males just because they are hateful mysoginistic beings or something like that, even when they are not. Queer people are still people after all, so they should probably have as many flaws as the non-queer people, and you should contemplate that into writing them as actual characters and not "that lesbian couple" in that game.
But people will always find a way to complain. This is a "damned if you do, damned if you don't" situation in which incorporating LGBT characters or not, making them flawed or not, making it an extremely secondary trait or their whole personality, making them evil or good, making them stereotypical or not, will result in outrage from certain demographics. My advice is, just do whatever you think will be best for your game without thinking of sales, reviews or prohibitions, because there are not enough cotton gloves in the world to tackle these topics without offending anyone.
If all you want to know is whether this will boost sales or not, it all depends on your target. As people mentioned before, do you want this game not o be 18 or not? Do you plan on translating it to Russian and selling it there? Do you want to target hardcore gamers who most often than not despise preachy politics in their games? If the answer to any of these is "yes", you may want to just leave it as heavily implied at best. Do you want to target fans of JRPG, who are very likely to like Japanese media in general? As stupid as it seems, your best bet is sexualizing them (people will get mad about this, but if they are outside of your target demographic, it doesn't really matter). Otherwise, if you want to target a more casual (not in a bad sense, not even as in people who only play Candy Crush on their phones - still "core" gamers, just not as fixated on videogames that take a lot of effort to play) or modern demographic, such as the people who played and liked Life is Strange, Gone Home, or Dragon Age: Inquisition, making them blatantly gay could even boost your sales.
EDIT: I remember Dofus had two NPC, a major and her secretary, named Mayor Cantille and Lou Bricante (yes, that's probably a sexual pun; game is full of them), who were very explicitly implicitly closet lesbians for each other. People talked a bit about this, but nobody seemed to care because it was cute and both girls were cute. Villagers would often gossip about it for comedic purposes. It wasn't given much relevance, and it was always treated in a very lighthearted tone -like the rest of the game-, so it simply happened to be a very secondary side story that was consistent with the setting, so I guess people simply accepted it; which brings me to the point that, if it is not a relevant plot point, just mention it in passing just like you would comment on any plot point of little relevancy.
I guess your case with the consul could be similar, but keep in mind that, depending on how directly based on Roman society the society in your game is, some people could complain about lack of realism (yeah, even if otherwise your game contains dragons and magic crystals). While ancient Rome didn't really treat homosexual relationships much differently to heterosexual relationships, they did treat women, and whoever they deemed to fulfill the role of the woman in a relationship, as inferior. I am unsure how would have ancient Rome reacted to a masculine lesbian consul, considering information on lesbians in ancient Rome is scarce, but chances are she would have stood no chance against other male politicians.
To avoid these complaints, either try to show (don't just tell!) in which ways this society distanced itself from our ancient Rome, and try to justify how could this happen, and of course, what could the possible reactions to this be, or just treat it in a consistent manner (if it isn't something people usually accept, why would they be telling anyone but people they utterly trust?).
Part of why people disliked the transsexual character in Baldur's Gate: Siege of Dragonspear is because they were out of place. It's already weird enough to bump into a stranger and casually start talking about stuff, so don't make it any weirder by talking about personal stuff most people have no bussiness knowing. This, combined by the fact that it just comes out of the blue (shoehorning), that the universe has genderbending magic that's apparently not in play here (inconsistency), that the topic isn't relevant at all to the plot or worldbuilding at al (virtue signaling at its finest), and that it's one of the only dialogues that doesn't let you any agency at all on how to react to this (which comes out as inconsistent, preachy and gives the impression Mizhena is above other characters just because she is trans) made several people, including trans people themselves, angry about the inclusion of just a token LGBT character for the sake of having a token LGBT character, above the normal rules of the world and dialog mechanics.