We were told in March that each available companion was being given specific, new dialog and story for same-gender romance. Perhaps this is in part to establish the character as specifically so inclined for purposes of that relationship. Thus, opposite-gender romance Corso (for example) becomes in effect a distinct character from same-gender romance Corso. I'd call this "herosexual, done right". The core persona need not change at all to accomodate orientation if the story holds up in both available options.
Well, if SGRs are indeed delivered with Makeb, which will be a class story extension (new level cap and all), I don't think it's far fetched to hope that companions' stories will be extended as well. If that's the case, voice actors that have already done the current romance stuff could record the necessary changes to have those romance available for same gender as well. Here's hoping.