Will everyone tend to pursue friendships/romance/marriage with NPCs who are tough, hardened adventurers, thieves, mages, warriors, archers, etc?
Or will you go for the bonny lass who serves pints at the local watering hole, or the baker's fair daughter?
Or would you be more interested in the Jarl's widow, or the general of the Rebel army, perhaps?
I hope for all of these and even more variations. I also hope that the mechanic doesn't end at marriage and move in. I'd like other NPC's to notice the change for starters, and if the spouse is the non-adventuring type I'd like to see that they still have lives and interact with the world. Instead of disappearing into my house and never seeing the light of day again, I'd like to see them go out to the market or the tavern, interact with other NPC's, friends and such. Maybe even (depending on the spouses personality, disposition, character archetype, etc.) have them get into a little bit of trouble themselves. Imagine having to bust your spouse out of jail for theft and bar-brawls and such, or rescuing them from kidnappers or bandits or something.