I think it'll be neat if they someday make a butch lesbian romance option. There's nobody in DA:I who would really fit that, other than maaaaaybe Cassie (who is still a bit more conventionally feminine than I associate with that label), who turned out to be straight.
Not to over-fixate on butch/femme dynamics or anything, but all of the same sex love interests they've ever provided for females - silk fox, liara, kelly, traynor, merrill, isabella - are pretty distinctly feminine, presumably because they are also supposed to appeal to straight males. Throwing a butch character into the mix would be a nice show of diversity along with addressing some of the "bioware is only so accommodating to lesbian romances because their male audience thinks girl-on-girl is hot" thing.
While appealing to men is likely a large part of it, I would have to disagree that it is a key appeal. I'm a woman myself, and have a huge preference for femme/femme couples, so Bioware's design choices suit me just fine. To me though, I'd think that a genuinely feminine woman, would be something like, one who is all dresses all the time, a flower in hair, whilst waiting for either a charming tough-ass femme and/or butch to sweep her off her feet. Truth be told, the charming tough-ass femme/feminine woman would be my favorite type of female coupling. 
However, none of the female characters you pointed out, even Merril, are any of that sort. They are all tough and independent in their own right, with Isabella, for example, kind of "a little butch" on the inside, despite the seemingly "femmy" appearence. That said, I do agree that more diversity could always be used, to provide a greater variety of romantic options for everyone. 