Way I see it, all but a handful of the companions would not be able to pull off a same gender relation.
Vette for example, although I'd love to see, seems to be the type who'll never taste the sweet sugar lips of another vixen - whereas Elara Dorne could easily pull off being a Dyke.
I'm looking forward to the same gender relations, not to mention all the content coming for companions... after completely finishing my trooper... it became kinda boring.
I still see Vette as a possible "I never considered being with a woman until you" type. You know the relatively new saying: "Love doesn't care about gender". I think it could easily be worked in with Vette and some others.