I started this game with my partner because of the marriage systems. We were able to live out something in a fake world that is denied to us. However, me and him both pick very attractive male elvaans... we then found out we couldnt marry. He could marry my mule.... or I could marry his... but never together...
Fable and the Sims are two games that come to my mind that allow you marry whichever sex you want... and then there is Grand Theft Auto which kids play that has a sex scene...
If this game had to get a higher game rating in the US because of same-sex marriage, I'm all for it. States are slowly responding to their constituents and voting approval on Same-Sex marriages.... Marriage is allowed for all in 10 countries, 6 states and Recognized in 6 countries and 3 states...
Most of the play base that I know of would not have a problem with the idea - plus I agree that there would not be much technical game mechanics that would have to change to allow it to happen.