Making Kira into a bisexual woman would, for example, not just be a matter of changing how she reacts to the female PC but also, in theory, every significant female NPC in the game. That means a lot more in the way of dialogue changes.
I think it depends on the character/female NPC.
As of today, Kira doesn't show interest in any male NPC, so I don't know why she'd have to start flirting with every female NPC if they opened her romance up to a female. As I mentioned before, I (as a female Jedi Knight) know nothing about her sexual preferences (she could be wookiesexual for all I know).
Using my fave example, Kaliyo, now it would make more sense to add them in for her character arc since she can be a flirt....heck, I think she was kinda flirting with Ensign Temple when I recruited her XD