I honestly wouldn't care.
I don't give much of a Shyte about how much Blood and Gore and Stuff is displayed, I can totally live without it.
I also don't think constant swearing adds much to a Character and if it has to be, you can just as easy use made-up words and tell everyone that's Future-Slang.
And finally (keep in Mind, this is only a personal and not entirely rational Opinion) I feel it has more Class, if they don't show Nudity and just fade to black.
And - voilá, there's a T-rating with the Game's Story not in any significant Way influenced, enabling BioWare to sell more of their Games, making more Money, which enables them in Turn to make more of their Games I have all enjoyed thus far.
So, I'm indifferent or even slightly positive to the Idea of making a T-rated BioWare Game.
Well, actually, we would lose some things most likely. For one, most T-rated games? You wouldn't get sex with your LI at all, not with all of the other aspects of the game that would push at the limits of what is acceptable for a T-rated game. Not just "fade to black," but "nothing more than a kiss." I would kind of be okay with that, myself, because I think "sex is a reward and the end goal" is a bit... off, in terms of what romance actually should be, which is making the player feel particularly connected to that romanced character.
As others have said, you probably wouldn't be making decisions where you shove someone out a window etc.
I have nothing against Teen rated games. I've played a lot of them, mostly JRPGs and Okami etc. Some of them are great, actually. Others less so. And in some cases, you could argue that the things that make certain games rated Mature, actually make the content of the game very immature. There was a time that, because of my mistaken impression of what an M-rated game actually was, I would have refused to play one.
I don't think ME or DA would lose much if they were reduced in rating, but as others have said, it would limit the developers' freedom more. Think of what you can do in a PG-13 movie, vs. a movie that is rated R. That's the difference between Rated T and Rated M--although I think a rated R movie can actually get away with more than a rated M game can, likely due to concerns about games' interactivity.
For ME and DA, though, I think they actually genuinely are mature games. Some 13-year-olds could handle them, but it's pretty clear that isn't the intended audience. You've got grown-up protagonists (30+ years old, even!), who deal with grown-up situations and enter into grown-up relationships (and we're not just talking about romance, but also friendships, comeraderie, etc.). While the protagonist and surrounding cast could probably stay the same age even if the game were to be given a lower rating, their behavior would have to be toned down to a level acceptable by parents of 13 year olds.
Some examples of things you probably wouldn't be able to have in a teen rated game: Exotic dancers, Chora's Den, sex with your LI unless heavily censored (still surprised Sims games' sex doesn't bump them to an M rating, but they are nonviolent...), heavy use of profanity, exploding heads from headshots, persistent gore, active murder of your enemies (or non-enemies).
I'm not sure about this, but they might also not be able to include LGBT romance options, were the game's rating reduced to Teen. So, you MIGHT only see straight love interests in a game that's rated Teen. A lot of times, I think that LGBT content can bump up the ratings. But again, I'm not sure about that.
I don't need sex scenes, and I don't need gore to prove that I'm grown up. I don't particularly enjoy the strip club scenes (seriously, Bioware, where are the nearly-naked male dancers????) and I don't hire the asari consort or spend my hard-earned gold at the brothels in Dragon Age games.
Nevertheless, I think a lot of that M-rated content does set the tone for the worlds the games are set in, and I think the Mature rating is important to give the developers free rein to make their game worlds/universes the way they want to. And, the average gamer is now in their 30s. I'm pretty sure that most of us can handle the Mature-rated content--granted, I could live without a lot of it, but I can also live with it. Sometimes we need to be taken out of our comfort zones, and a game is a safe way to do that.
While I think it's important that there are games for younger audiences available, I also think it's important to have games that are actually made with adult players in mind--games that can contain this kind of gritty content and treat it seriously and treat things like relationships and sex seriously, too. Yeah, I know that BioWare games aren't 100% serious 100% of the time. They are, after all, games, which we play for fun. But they are games with a lot of material to think about, in their lore and in their plots and side quests.
So no, even though I'm fine with "cleaner" content, I would prefer that Dragon Age and Mass Effect both remain Mature rated.
I'd be okay with some new IP of theirs being more teen-friendly though. And I'd probably still play it.