To be honest: I've longed for a gay/bisexual KISA in a Bioware Game for so long that I think this is what it's all about:
Longing for something because you cannot have it.
I think if they really added a gay/bi KISA I'd find him far less interesting that I'd imagine him to be now.
Would I really choose a gay/bi Alistair or Sebastian or Cullen over Anders, Fenris, Dorian, Kaidan?
I doubt that. Bioware has given us many interesting bisexual/gay companions so far.
I do not disapprove of this idea however. It would be nice to see one gay/bi KISA for once and then
see if I would be really excited or if I just wanted him because I couldn't have him.
I think it's a bit of both. Even if those characters were romancable by men, Dorian and Kaidan would still be my top two, and Sebastian couldn't get me if he was the last man alive, but Alistair and Cullen would both easily beat out Zevran, Fenris, Steve, and Bull for me. Probably even Anders, although I do genuinely enjoy him as a love interest unlike the others.
Anyway, it would be nice to have the option. Even if I would end up choosing Dorian over Cullen nine times out of ten, I would appreciate Dragon Age offering a queer character who isn't an inherent outcast, which isn't exactly the same as the KISA dichotomy, but it does bother me that if you put DA's queer characters all in the same area, it looks like the island of misfit toys with the exception of Josephine.